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Harter TS, Smith EA, Salmerón C, Thies AB, Delgado B, Wilson RW, Tresguerres M. Soluble adenylyl cyclase is an acid-base sensor in rainbow trout red blood cells that regulates intracellular pH and haemoglobin-oxygen binding. Acta Physiol (Oxf) 2024:e14205. [PMID: 39031444 DOI: 10.1111/apha.14205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Revised: 06/12/2024] [Accepted: 07/04/2024] [Indexed: 07/22/2024]
Abstract
AIM To identify the physiological role of the acid-base sensing enzyme, soluble adenylyl cyclase (sAC), in red blood cells (RBC) of the model teleost fish, rainbow trout. METHODS We used: (i) super-resolution microscopy to determine the subcellular location of sAC protein; (ii) live-cell imaging of RBC intracellular pH (pHi) with specific sAC inhibition (KH7 or LRE1) to determine its role in cellular acid-base regulation; (iii) spectrophotometric measurements of haemoglobin-oxygen (Hb-O2) binding in steady-state conditions; and (iv) during simulated arterial-venous transit, to determine the role of sAC in systemic O2 transport. RESULTS Distinct pools of sAC protein were detected in the RBC cytoplasm, at the plasma membrane and within the nucleus. Inhibition of sAC decreased the setpoint for RBC pHi regulation by ~0.25 pH units compared to controls, and slowed the rates of RBC pHi recovery after an acid-base disturbance. RBC pHi recovery was entirely through the anion exchanger (AE) that was in part regulated by HCO3 --dependent sAC signaling. Inhibition of sAC decreased Hb-O2 affinity during a respiratory acidosis compared to controls and reduced the cooperativity of O2 binding. During in vitro simulations of arterial-venous transit, sAC inhibition decreased the amount of O2 that is unloaded by ~11%. CONCLUSION sAC represents a novel acid-base sensor in the RBCs of rainbow trout, where it participates in the modulation of RBC pHi and blood O2 transport though the regulation of AE activity. If substantiated in other species, these findings may have broad implications for our understanding of cardiovascular physiology in vertebrates.
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Affiliation(s)
- Till S Harter
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA
| | - Emma A Smith
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA
| | - Cristina Salmerón
- Department of Pharmacology, University of California San Diego, La Jolla, California, USA
| | - Angus B Thies
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA
| | - Bryan Delgado
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA
| | - Rod W Wilson
- Biosciences Department, College of Life and Environmental Sciences, University of Exeter, Exeter, UK
| | - Martin Tresguerres
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA
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2
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Becker HM, Seidler UE. Bicarbonate secretion and acid/base sensing by the intestine. Pflugers Arch 2024; 476:593-610. [PMID: 38374228 PMCID: PMC11006743 DOI: 10.1007/s00424-024-02914-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Revised: 01/15/2024] [Accepted: 01/17/2024] [Indexed: 02/21/2024]
Abstract
The transport of bicarbonate across the enterocyte cell membrane regulates the intracellular as well as the luminal pH and is an essential part of directional fluid movement in the gut. Since the first description of "active" transport of HCO3- ions against a concentration gradient in the 1970s, the fundamental role of HCO3- transport for multiple intestinal functions has been recognized. The ion transport proteins have been identified and molecularly characterized, and knockout mouse models have given insight into their individual role in a variety of functions. This review describes the progress made in the last decade regarding novel techniques and new findings in the molecular regulation of intestinal HCO3- transport in the different segments of the gut. We discuss human diseases with defects in intestinal HCO3- secretion and potential treatment strategies to increase luminal alkalinity. In the last part of the review, the cellular and organismal mechanisms for acid/base sensing in the intestinal tract are highlighted.
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Affiliation(s)
- Holger M Becker
- Department of Gastroenterology, Hannover Medical School, 30625, Hannover, Germany
| | - Ursula E Seidler
- Department of Gastroenterology, Hannover Medical School, 30625, Hannover, Germany.
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3
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Localization of the Neuropeptide Arginine Vasotocin and Its Receptor in the Osmoregulatory Organs of Black Porgy, Acanthopagrus schlegelii: Gills, Kidneys, and Intestines. Int J Mol Sci 2022; 23:ijms232113421. [DOI: 10.3390/ijms232113421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 10/26/2022] [Accepted: 10/28/2022] [Indexed: 11/06/2022] Open
Abstract
The neurohypophysial hormone arginine vasotocin (avt) and its receptor (avtr) regulates ions in the osmoregulatory organs of euryhaline black porgy (Acanthopagrus schlegelii). The localization of avt and avtr transcripts in the osmoregulatory organs has yet to be demonstrated. Thus, in the present study, we performed an in situ hybridization analysis to determine the localization of avt and avtr in the gills, kidneys, and intestines of the black porgy. The avt and avtr transcripts were identified in the filament and lamellae region of the gills in the black porgy. However, the basal membrane of the filament contained more avt and avtr transcripts. Fluorescence double tagging analysis revealed that avt and avtr mRNAs were partially co-localized with α-Nka-ir cells in the gill filament. The proximal tubules, distal tubules, and collecting duct of the kidney all had positive hybridization signals for the avt and avtr transcripts. Unlike the α-Nka immunoreactive cells, the avt and avtr transcripts were found on the basolateral surface of the distal convoluted tubule and in the entire cells of the proximal convoluted tubules of the black porgy kidney. In the intestine, the avt and avtr transcripts were found in the basolateral membrane of the enterocytes. Collectively, this study provides a summary of evidence suggesting that the neuropeptides avt and avtr with α-Nka-ir cells may have functions in the gills, kidneys, and intestines via ionocytes.
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Kwan GT, Frable BW, Thompson AR, Tresguerres M. Optimizing immunostaining of archival fish samples to enhance museum collection potential. Acta Histochem 2022; 124:151952. [PMID: 36099745 DOI: 10.1016/j.acthis.2022.151952] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 08/31/2022] [Accepted: 09/04/2022] [Indexed: 11/18/2022]
Abstract
Immunohistochemistry (IHC) is a powerful biochemical technique that uses antibodies to specifically label and visualize proteins of interests within biological samples. However, fluid-preserved specimens within natural history collection often use fixatives and protocols that induce high background signal (autofluorescence), which hampers IHC as it produces low signal-to-noise ratio. Here, we explored techniques to reduce autofluorescence using sodium borohydride (SBH), citrate buffer, and their combination on fish tissue preserved with paraformaldehyde, formaldehyde, ethanol, and glutaraldehyde. We found SBH was the most effective quenching technique, and applied this pretreatment to the gill or skin of 10 different archival fishes - including specimens that had been preserved in formaldehyde or ethanol for up to 65 and 37 years, respectively. The enzyme Na+/K+-ATPase (NKA) was successfully immunostained and imaged using confocal fluorescence microscopy, allowing for the identification and characterization of NKA-rich ionocytes essential for fish ionic and acid-base homeostasis. Altogether, our SBH-based method facilitates the use of IHC on archival samples, and unlocks the historical record on fish biological responses to environmental factors (such as climate change) using specimens from natural history collections that were preserved decades to centuries ago.
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Affiliation(s)
- Garfield T Kwan
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, USA; NOAA Fisheries Service, Southwest Fisheries Science Center, La Jolla, CA, USA.
| | - Benjamin W Frable
- Marine Vertebrate Collection, Scripps Institution of Oceanography, University of California San Diego, USA
| | - Andrew R Thompson
- NOAA Fisheries Service, Southwest Fisheries Science Center, La Jolla, CA, USA
| | - Martin Tresguerres
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, USA
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5
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Barany A, Gilannejad N, Alameda-López M, Rodríguez-Velásquez L, Astola A, Martínez-Rodríguez G, Roo J, Muñoz JL, Mancera JM. Osmoregulatory Plasticity of Juvenile Greater Amberjack ( Seriola dumerili) to Environmental Salinity. Animals (Basel) 2021; 11:2607. [PMID: 34573573 PMCID: PMC8465821 DOI: 10.3390/ani11092607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2021] [Revised: 08/23/2021] [Accepted: 09/01/2021] [Indexed: 11/16/2022] Open
Abstract
Osmotic costs in teleosts are highly variable, reaching up to 50% of energy expenditure in some. In several species, environmental salinities close to the isosmotic point (~15 psu) minimize energy demand for osmoregulation while enhancing growth. The present study aimed to characterize the physiological status related to osmoregulation in early juveniles of the greater amberjack, Seriola dumerili, acclimated to three salinities (15, 22, and 36 psu). Our results indicate that plasma metabolic substrates were enhanced at the lower salinities, whereas hepatic carbohydrate and energetic lipid substrates decreased. Moreover, osmoregulatory parameters, such as osmolality, muscle water content, gill and intestine Na+-K+-ATPase activities, suggested a great osmoregulatory capacity in this species. Remarkably, electrophysiological parameters, such as short-circuit current (Isc) and transepithelial electric resistance (TER), were enhanced significantly at the posterior intestine. Concomitantly, Isc and TER anterior-to-posterior intestine differences were intensified with increasing environmental salinity. Furthermore, the expression of several adeno-hypophyseal genes was assessed. Expression of prl showed an inverse linear relationship with increasing environmental salinity, while gh mRNA enhanced significantly in the 22 psu-acclimated groups. Overall, these results could explain the better growth observed in S. dumerili juveniles kept at salinities close to isosmotic rather than in seawater.
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Affiliation(s)
- Andre Barany
- Department of Biology, Faculty of Marine and Environmental Sciences, Instituto Universitario de Investigación Marina (INMAR), Campus de Excelencia Internacional del Mar (CEI·MAR), University of Cádiz, Puerto Real, E11510 Cádiz, Spain; (M.A.-L.); (L.R.-V.); (J.M.M.)
| | - Neda Gilannejad
- Instituto de Ciencias Marinas de Andalucía, Consejo Superior de Investigaciones Científicas (ICMAN-CSIC), Puerto Real, E11519 Cádiz, Spain; (N.G.); (G.M.-R.)
- NORCE Norwegian Research Centre AS, Uni Research Environment, Nygårdsgaten 112, E5008 Bergen, Norway
| | - María Alameda-López
- Department of Biology, Faculty of Marine and Environmental Sciences, Instituto Universitario de Investigación Marina (INMAR), Campus de Excelencia Internacional del Mar (CEI·MAR), University of Cádiz, Puerto Real, E11510 Cádiz, Spain; (M.A.-L.); (L.R.-V.); (J.M.M.)
| | - Liliana Rodríguez-Velásquez
- Department of Biology, Faculty of Marine and Environmental Sciences, Instituto Universitario de Investigación Marina (INMAR), Campus de Excelencia Internacional del Mar (CEI·MAR), University of Cádiz, Puerto Real, E11510 Cádiz, Spain; (M.A.-L.); (L.R.-V.); (J.M.M.)
| | - Antonio Astola
- Department of Biomedicine, Biotechnology, and Public Health, Faculty of Sciences, Campus de Excelencia Internacional del Mar (CEI-MAR), University of Cadiz, Puerto Real, E11510 Cádiz, Spain;
| | - Gonzalo Martínez-Rodríguez
- Instituto de Ciencias Marinas de Andalucía, Consejo Superior de Investigaciones Científicas (ICMAN-CSIC), Puerto Real, E11519 Cádiz, Spain; (N.G.); (G.M.-R.)
| | - Javier Roo
- Grupo de Investigación en Acuicultura (GIA), Instituto Universitario Ecoaqua, Universidad de Las Palmas de Gran Canaria, Crta. Taliarte s/n, E35214 Gran Canaria, Spain;
| | - Jose Luis Muñoz
- Department of Production, IFAPA Centro “El Toruño”, Junta de Andalucía, El Puerto de Santa María, E11500 Cádiz, Spain;
| | - Juan Miguel Mancera
- Department of Biology, Faculty of Marine and Environmental Sciences, Instituto Universitario de Investigación Marina (INMAR), Campus de Excelencia Internacional del Mar (CEI·MAR), University of Cádiz, Puerto Real, E11510 Cádiz, Spain; (M.A.-L.); (L.R.-V.); (J.M.M.)
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6
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Takei Y. The digestive tract as an essential organ for water acquisition in marine teleosts: lessons from euryhaline eels. ZOOLOGICAL LETTERS 2021; 7:10. [PMID: 34154668 PMCID: PMC8215749 DOI: 10.1186/s40851-021-00175-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Accepted: 04/16/2021] [Indexed: 05/17/2023]
Abstract
Adaptation to a hypertonic marine environment is one of the major topics in animal physiology research. Marine teleosts lose water osmotically from the gills and compensate for this loss by drinking surrounding seawater and absorbing water from the intestine. This situation is in contrast to that in mammals, which experience a net osmotic loss of water after drinking seawater. Water absorption in fishes is made possible by (1) removal of monovalent ions (desalinization) by the esophagus, (2) removal of divalent ions as carbonate (Mg/CaCO3) precipitates promoted by HCO3- secretion, and (3) facilitation of NaCl and water absorption from diluted seawater by the intestine using a suite of unique transporters. As a result, 70-85% of ingested seawater is absorbed during its passage through the digestive tract. Thus, the digestive tract is an essential organ for marine teleost survival in the hypertonic seawater environment. The eel is a species that has been frequently used for osmoregulation research in laboratories worldwide. The eel possesses many advantages as an experimental animal for osmoregulation studies, one of which is its outstanding euryhalinity, which enables researchers to examine changes in the structure and function of the digestive tract after direct transfer from freshwater to seawater. In recent years, the molecular mechanisms of ion and water transport across epithelial cells (the transcellular route) and through tight junctions (the paracellular route) have been elucidated for the esophagus and intestine. Thanks to the rapid progress in analytical methods for genome databases on teleosts, including the eel, the molecular identities of transporters, channels, pumps and junctional proteins have been clarified at the isoform level. As 10 y have passed since the previous reviews on this subject, it seems relevant and timely to summarize recent progress in research on the molecular mechanisms of water and ion transport in the digestive tract in eels and to compare the mechanisms with those of other teleosts and mammals from comparative and evolutionary viewpoints. We also propose future directions for this research field to achieve integrative understanding of the role of the digestive tract in adaptation to seawater with regard to pathways/mechanisms including the paracellular route, divalent ion absorption, metabolon formation and cellular trafficking of transporters. Notably, some of these have already attracted practical attention in laboratories.
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Affiliation(s)
- Yoshio Takei
- Laboratory of Physiology, Department of Marine Bioscience, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8564, Japan.
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7
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Salmerón C, Harter TS, Kwan GT, Roa JN, Blair SD, Rummer JL, Shiels HA, Goss GG, Wilson RW, Tresguerres M. Molecular and biochemical characterization of the bicarbonate-sensing soluble adenylyl cyclase from a bony fish, the rainbow trout Oncorhynchus mykiss. Interface Focus 2021; 11:20200026. [PMID: 33633829 DOI: 10.1098/rsfs.2020.0026] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/09/2020] [Indexed: 12/14/2022] Open
Abstract
Soluble adenylyl cyclase (sAC) is a HC O 3 - -stimulated enzyme that produces the ubiquitous signalling molecule cAMP, and deemed an evolutionarily conserved acid-base sensor. However, its presence is not yet confirmed in bony fishes, the most abundant and diverse of vertebrates. Here, we identified sAC genes in various cartilaginous, ray-finned and lobe-finned fish species. Next, we focused on rainbow trout sAC (rtsAC) and identified 20 potential alternative spliced mRNAs coding for protein isoforms ranging in size from 28 to 186 kDa. Biochemical and kinetic analyses on purified recombinant rtsAC protein determined stimulation by HC O 3 - at physiologically relevant levels for fish internal fluids (EC50 ∼ 7 mM). rtsAC activity was sensitive to KH7, LRE1, and DIDS (established inhibitors of sAC from other organisms), and insensitive to forskolin and 2,5-dideoxyadenosine (modulators of transmembrane adenylyl cyclases). Western blot and immunocytochemistry revealed high rtsAC expression in gill ion-transporting cells, hepatocytes, red blood cells, myocytes and cardiomyocytes. Analyses in the cell line RTgill-W1 suggested that some of the longer rtsAC isoforms may be preferentially localized in the nucleus, the Golgi apparatus and podosomes. These results indicate that sAC is poised to mediate multiple acid-base homeostatic responses in bony fishes, and provide cues about potential novel functions in mammals.
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Affiliation(s)
- Cristina Salmerón
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA.,Department of Pharmacology, University of California San Diego, San Diego, CA, USA
| | - Till S Harter
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA
| | - Garfield T Kwan
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA
| | - Jinae N Roa
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA
| | - Salvatore D Blair
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.,Department of Biology, Winthrop University, Rock Hill, SC, USA
| | - Jodie L Rummer
- Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland, Australia
| | - Holly A Shiels
- Division of Cardiovascular Sciences, Faculty of Biology, Medicine and Health, University of Manchester, UK
| | - Greg G Goss
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Rod W Wilson
- Department of Biosciences, University of Exeter, Exeter, UK
| | - Martin Tresguerres
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA
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8
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Kwan GT, Smith TR, Tresguerres M. Immunological characterization of two types of ionocytes in the inner ear epithelium of Pacific Chub Mackerel (Scomber japonicus). J Comp Physiol B 2020; 190:419-431. [PMID: 32468089 DOI: 10.1007/s00360-020-01276-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 01/20/2020] [Accepted: 03/30/2020] [Indexed: 12/14/2022]
Abstract
The inner ear is essential for maintaining balance and hearing predator and prey in the environment. Each inner ear contains three CaCO3 otolith polycrystals, which are calcified within an alkaline, K+-rich endolymph secreted by the surrounding epithelium. However, the underlying cellular mechanisms are poorly understood, especially in marine fish. Here, we investigated the presence and cellular localization of several ion-transporting proteins within the saccular epithelium of the Pacific Chub Mackerel (Scomber japonicus). Western blotting revealed the presence of Na+/K+-ATPase (NKA), carbonic anhydrase (CA), Na+-K+-2Cl--co-transporter (NKCC), vacuolar-type H+-ATPase (VHA), plasma membrane Ca2+ ATPase (PMCA), and soluble adenylyl cyclase (sAC). Immunohistochemistry analysis identified two distinct ionocytes types in the saccular epithelium: Type-I ionocytes were mitochondrion-rich and abundantly expressed NKA and NKCC in their basolateral membrane, indicating a role in secreting K+ into the endolymph. On the other hand, Type-II ionocytes were enriched in cytoplasmic CA and VHA, suggesting they help transport HCO3- into the endolymph and remove H+. In addition, both types of ionocytes expressed cytoplasmic PMCA, which is likely involved in Ca2+ transport and homeostasis, as well as sAC, an evolutionary conserved acid-base sensing enzyme that regulates epithelial ion transport. Furthermore, CA, VHA, and sAC were also expressed within the capillaries that supply blood to the meshwork area, suggesting additional mechanisms that contribute to otolith calcification. This information improves our knowledge about the cellular mechanisms responsible for endolymph ion regulation and otolith formation, and can help understand responses to environmental stressors such as ocean acidification.
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Affiliation(s)
- Garfield T Kwan
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, USA
| | - Taylor R Smith
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, USA
| | - Martin Tresguerres
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, USA.
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9
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Tresguerres M, Clifford AM, Harter TS, Roa JN, Thies AB, Yee DP, Brauner CJ. Evolutionary links between intra- and extracellular acid-base regulation in fish and other aquatic animals. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2020; 333:449-465. [PMID: 32458594 DOI: 10.1002/jez.2367] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 03/10/2020] [Accepted: 05/06/2020] [Indexed: 12/17/2022]
Abstract
The acid-base relevant molecules carbon dioxide (CO2 ), protons (H+ ), and bicarbonate (HCO3 - ) are substrates and end products of some of the most essential physiological functions including aerobic and anaerobic respiration, ATP hydrolysis, photosynthesis, and calcification. The structure and function of many enzymes and other macromolecules are highly sensitive to changes in pH, and thus maintaining acid-base homeostasis in the face of metabolic and environmental disturbances is essential for proper cellular function. On the other hand, CO2 , H+ , and HCO3 - have regulatory effects on various proteins and processes, both directly through allosteric modulation and indirectly through signal transduction pathways. Life in aquatic environments presents organisms with distinct acid-base challenges that are not found in terrestrial environments. These include a relatively high CO2 relative to O2 solubility that prevents internal CO2 /HCO3 - accumulation to buffer pH, a lower O2 content that may favor anaerobic metabolism, and variable environmental CO2 , pH and O2 levels that require dynamic adjustments in acid-base homeostatic mechanisms. Additionally, some aquatic animals purposely create acidic or alkaline microenvironments that drive specialized physiological functions. For example, acidifying mechanisms can enhance O2 delivery by red blood cells, lead to ammonia trapping for excretion or buoyancy purposes, or lead to CO2 accumulation to promote photosynthesis by endosymbiotic algae. On the other hand, alkalinizing mechanisms can serve to promote calcium carbonate skeletal formation. This nonexhaustive review summarizes some of the distinct acid-base homeostatic mechanisms that have evolved in aquatic organisms to meet the particular challenges of this environment.
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Affiliation(s)
- Martin Tresguerres
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, California
| | - Alexander M Clifford
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, California
| | - Till S Harter
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, California
| | - Jinae N Roa
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, California
| | - Angus B Thies
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, California
| | - Daniel P Yee
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, California
| | - Colin J Brauner
- Department of Zoology, University of British Columbia, Vancouver, Canada
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10
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Regulation of coral calcification by the acid-base sensing enzyme soluble adenylyl cyclase. Biochem Biophys Res Commun 2020; 525:576-580. [PMID: 32115151 DOI: 10.1016/j.bbrc.2020.02.115] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Accepted: 02/19/2020] [Indexed: 02/06/2023]
Abstract
Coral calcification is intricately linked to the chemical composition of the fluid in the extracellular calcifying medium (ECM), which is situated between the calcifying cells and the skeleton. Here we demonstrate that the acid-base sensing enzyme soluble adenylyl cyclase (sAC) is expressed in calcifying cells of the coral Stylophora pistillata. Furthermore, pharmacological inhibition of sAC in coral microcolonies resulted in acidification of the ECM as estimated by the pH-sensitive ratiometric indicator SNARF, and decreased calcification rates, as estimated by calcein labeling of crystal growth. These results indicate that sAC activity modulates some of the molecular machinery involved in producing the coral skeleton, which could include ion-transporting proteins and vesicular transport. To our knowledge this is the first study to directly demonstrate biological regulation of the alkaline pH of the coral ECM and its correlation with calcification.
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11
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Espejo MS, Orlowski A, Ibañez AM, Di Mattía RA, Velásquez FC, Rossetti NS, Ciancio MC, De Giusti VC, Aiello EA. The functional association between the sodium/bicarbonate cotransporter (NBC) and the soluble adenylyl cyclase (sAC) modulates cardiac contractility. Pflugers Arch 2019; 472:103-115. [PMID: 31754830 DOI: 10.1007/s00424-019-02331-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 10/15/2019] [Accepted: 11/13/2019] [Indexed: 12/21/2022]
Abstract
The soluble adenylyl cyclase (sAC) was identified in the heart as another source of cyclic AMP (cAMP). However, its cardiac physiological function is unknown. On the other hand, the cardiac Na+/HCO3- cotransporter (NBC) promotes the cellular co-influx of HCO3- and Na+. Since sAC activity is regulated by HCO3-, our purpose was to investigate the potential functional relationship between NBC and sAC in the cardiomyocyte. Rat ventricular myocytes were loaded with Fura-2, Fluo-3, or BCECF to measure Ca2+ transient (Ca2+i) by epifluorescence, Ca2+ sparks frequency (CaSF) by confocal microscopy, or intracellular pH (pHi) by epifluorescence, respectively. Sarcomere or cell shortening was measured with a video camera as an index of contractility. The NBC blocker S0859 (10 μM), the selective inhibitor of sAC KH7 (1 μM), and the PKA inhibitor H89 (0.1 μM) induced a negative inotropic effect which was associated with a decrease in Ca2+i. Since PKA increases Ca2+ release through sarcoplasmic reticulum RyR channels, CaSF was measured as an index of RyR open probability. The generation of CaSF was prevented by KH7. Finally, we investigated the potential role of sAC activation on NBC activity. NBC-mediated recovery from acidosis was faster in the presence of KH7 or H89, suggesting that the pathway sAC-PKA is negatively regulating NBC function, consistent with a negative feedback modulation of the HCO3- influx that activates sAC. In summary, the results demonstrated that the complex NBC-sAC-PKA plays a relevant role in Ca2+ handling and basal cardiac contractility.
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Affiliation(s)
- María S Espejo
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, Calle 60 y 120, 1900, La Plata, Argentina
| | - Alejandro Orlowski
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, Calle 60 y 120, 1900, La Plata, Argentina
| | - Alejandro M Ibañez
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, Calle 60 y 120, 1900, La Plata, Argentina
| | - Romina A Di Mattía
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, Calle 60 y 120, 1900, La Plata, Argentina
| | - Fernanda Carrizo Velásquez
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, Calle 60 y 120, 1900, La Plata, Argentina
| | - Noelia S Rossetti
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, Calle 60 y 120, 1900, La Plata, Argentina
| | - María C Ciancio
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, Calle 60 y 120, 1900, La Plata, Argentina
| | - Verónica C De Giusti
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, Calle 60 y 120, 1900, La Plata, Argentina.
| | - Ernesto A Aiello
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, Calle 60 y 120, 1900, La Plata, Argentina.
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12
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Barany A, Shaughnessy CA, Fuentes J, Mancera JM, McCormick SD. Osmoregulatory role of the intestine in the sea lamprey ( Petromyzon marinus). Am J Physiol Regul Integr Comp Physiol 2019; 318:R410-R417. [PMID: 31747320 DOI: 10.1152/ajpregu.00033.2019] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Lampreys are the most basal vertebrates with an osmoregulatory strategy. Previous research has established that the salinity tolerance of sea lamprey increases dramatically during metamorphosis, but underlying changes in the gut have not been examined. In the present work, we examined changes in intestinal function during metamorphosis and seawater exposure of sea lamprey (Petromyzon marinus). Fully metamorphosed juvenile sea lamprey had 100% survival after direct exposure to 35 parts per thousand seawater (SW) and only slight elevations in plasma chloride (Cl-) levels. Drinking rates of sea lamprey juveniles in seawater were 26-fold higher than juveniles in freshwater (FW). Na+-K+-ATPase (NKA) activity in the anterior and posterior intestine increased 12- and 3-fold, respectively, during metamorphosis, whereas esophageal NKA activity was lower than in the intestine and did not change with development. Acclimation to SW significantly enhanced NKA activity in the posterior intestine but did not significantly change NKA activity in the anterior intestine, which remained higher than that in the posterior intestine. Intestinal Cl- and water uptake, which were observed in ex vivo preparations of anterior and posterior intestine under both symmetric and asymmetric conditions, were higher in juveniles than in larvae and were similar in magnitude of those of teleost fish. Inhibition of NKA by ouabain in ex vivo preparations inhibited intestinal water absorption by 64%. Our results indicate drinking and intestinal ion and water absorption are important to osmoregulation in SW and that preparatory increases in intestinal NKA activity are important to the development of salinity tolerance that occurs during sea lamprey metamorphosis.
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Affiliation(s)
- A Barany
- Department of Biology, Faculty of Marine and Environmental Sciences, Campus de Excelencia Internacional del Mar, University of Cádiz, Cádiz, Spain.,Centre of Marine Sciences, University of Algarve, Gambelas, Faro, Portugal
| | - C A Shaughnessy
- United States Geological Survey, Leetown Science Center, S.O. Conte Anadromous Fish Research Laboratory, Turners Falls, Massachusetts
| | - J Fuentes
- Centre of Marine Sciences, University of Algarve, Gambelas, Faro, Portugal
| | - J M Mancera
- Department of Biology, Faculty of Marine and Environmental Sciences, Campus de Excelencia Internacional del Mar, University of Cádiz, Cádiz, Spain
| | - S D McCormick
- United States Geological Survey, Leetown Science Center, S.O. Conte Anadromous Fish Research Laboratory, Turners Falls, Massachusetts.,Graduate Program in Organismic and Evolutionary Biology, University of Massachusetts, Amherst, Massachusetts
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13
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Gregório SF, Ruiz-Jarabo I, Carvalho EM, Fuentes J. Increased intestinal carbonate precipitate abundance in the sea bream (Sparus aurata L.) in response to ocean acidification. PLoS One 2019; 14:e0218473. [PMID: 31226164 PMCID: PMC6588277 DOI: 10.1371/journal.pone.0218473] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Accepted: 06/03/2019] [Indexed: 12/20/2022] Open
Abstract
Marine fish contribute to the carbon cycle by producing mineralized intestinal precipitates generated as by-products of their osmoregulation. Here we aimed at characterizing the control of epithelial bicarbonate secretion and intestinal precipitate presence in the gilthead sea bream in response to predicted near future increases of environmental CO2. Our results demonstrate that hypercapnia (950 and 1800 μatm CO2) elicits higher intestine epithelial HCO3- secretion ex vivo and a subsequent parallel increase of intestinal precipitate presence in vivo when compared to present values (440 μatm CO2). Intestinal gene expression analysis in response to environmental hypercapnia revealed the up-regulation of transporters involved in the intestinal bicarbonate secretion cascade such as the basolateral sodium bicarbonate co-transporter slc4a4, and the apical anion transporters slc26a3 and slc26a6 of sea bream. In addition, other genes involved in intestinal ion uptake linked to water absorption such as the apical nkcc2 and aquaporin 1b expression, indicating that hypercapnia influences different levels of intestinal physiology. Taken together the current results are consistent with an intestinal physiological response leading to higher bicarbonate secretion in the intestine of the sea bream paralleled by increased luminal carbonate precipitate abundance and the main related transporters in response to ocean acidification.
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Affiliation(s)
- Sílvia F. Gregório
- Centre of Marine Sciences (CCMar), Universidade do Algarve, Campus de Gambelas, Faro, Portugal
| | - Ignacio Ruiz-Jarabo
- Centre of Marine Sciences (CCMar), Universidade do Algarve, Campus de Gambelas, Faro, Portugal
| | - Edison M. Carvalho
- Centre of Marine Sciences (CCMar), Universidade do Algarve, Campus de Gambelas, Faro, Portugal
| | - Juan Fuentes
- Centre of Marine Sciences (CCMar), Universidade do Algarve, Campus de Gambelas, Faro, Portugal
- * E-mail:
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14
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Alves A, Gregório SF, Egger RC, Fuentes J. Molecular and functional regionalization of bicarbonate secretion cascade in the intestine of the European sea bass (Dicentrarchus labrax). Comp Biochem Physiol A Mol Integr Physiol 2019; 233:53-64. [PMID: 30946979 DOI: 10.1016/j.cbpa.2019.03.017] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 03/20/2019] [Accepted: 03/25/2019] [Indexed: 10/27/2022]
Abstract
In marine fish the intestinal HCO3- secretion is the key mechanism to enable luminal aggregate formation and water absorption. Using the sea bass (Dicentrarchus labrax), the present study aimed at establishing the functional and molecular organization of different sections of the intestine concerning bicarbonate secretion and Cl- movements. The proximal intestinal regions presented similar HCO3- secretion rates, while differences were detected in the molecular expression of the transporters involved and on regional HCO3- concentrations. The anterior region presented significantly higher Na+/K+-ATPase activity, Cl- transepithelial transport and basolateral slc4a4, apical slc26a6 and slc26a3 expression levels. In the mid intestine, the total HCO3- content was significantly increased in the fluid as in the carbonate aggregates. In the rectum no HCO3- secretion was observed and was characterized by the diminished HCO3- total content, residual molecular expression of slc4a4, slc26a6 and slc26a3, higher H+-ATPase activity and expression, suggesting the existence of a different bicarbonate handling mechanism. The possible regulation of HCO3- secretion by extracellular HCO3- and increased intracellular cAMP levels were also investigated. cAMP did not affect HCO3- secretion, although Cl- secretion was enhanced by cftr. HCO3- secretion rise due to the HCO3- basolateral increment showed that at resting levels slc4a4 was not a limiting step for secretion. The transcellular/intracellular dependence of apical HCO3- secretion differed between the proximal regions. In conclusion, intestinal HCO3- secretion has a functional region-dependent organization that was not reflected by the anterior-posterior regionalization on HCO3- secretion and expression profiles of chloride/water absorption related genes.
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Affiliation(s)
- Alexandra Alves
- Centre of Marine Sciences (CCMAR), University of Algarve, Campus de Gambelas, 8005-139 Faro, Portugal
| | - Sílvia F Gregório
- Centre of Marine Sciences (CCMAR), University of Algarve, Campus de Gambelas, 8005-139 Faro, Portugal
| | - Renata C Egger
- Centre of Marine Sciences (CCMAR), University of Algarve, Campus de Gambelas, 8005-139 Faro, Portugal
| | - Juan Fuentes
- Centre of Marine Sciences (CCMAR), University of Algarve, Campus de Gambelas, 8005-139 Faro, Portugal.
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15
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Wiggins SV, Steegborn C, Levin LR, Buck J. Pharmacological modulation of the CO 2/HCO 3-/pH-, calcium-, and ATP-sensing soluble adenylyl cyclase. Pharmacol Ther 2018; 190:173-186. [PMID: 29807057 DOI: 10.1016/j.pharmthera.2018.05.008] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Cyclic AMP (cAMP), the prototypical second messenger, has been implicated in a wide variety of (often opposing) physiological processes. It simultaneously mediates multiple, diverse processes, often within a single cell, by acting locally within independently-regulated and spatially-restricted microdomains. Within each microdomain, the level of cAMP will be dependent upon the balance between its synthesis by adenylyl cyclases and its degradation by phosphodiesterases (PDEs). In mammalian cells, there are many PDE isoforms and two types of adenylyl cyclases; the G protein regulated transmembrane adenylyl cyclases (tmACs) and the CO2/HCO3-/pH-, calcium-, and ATP-sensing soluble adenylyl cyclase (sAC). Discriminating the roles of individual cyclic nucleotide microdomains requires pharmacological modulators selective for the various PDEs and/or adenylyl cyclases. Such tools present an opportunity to develop therapeutics specifically targeted to individual cAMP dependent pathways. The pharmacological modulators of tmACs have recently been reviewed, and in this review, we describe the current status of pharmacological tools available for studying sAC.
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Affiliation(s)
- Shakarr V Wiggins
- Graduate Program in Neuroscience, Weill Cornell Medicine, New York, NY 10065, United States
| | - Clemens Steegborn
- Department of Biochemistry, University of Bayreuth, 95440 Bayreuth, Germany
| | - Lonny R Levin
- Department of Pharmacology, Weill Cornell Medicine, New York, NY 10065, United States.
| | - Jochen Buck
- Department of Pharmacology, Weill Cornell Medicine, New York, NY 10065, United States
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16
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Molecular, Enzymatic, and Cellular Characterization of Soluble Adenylyl Cyclase From Aquatic Animals. Methods Enzymol 2018; 605:525-549. [PMID: 29909838 DOI: 10.1016/bs.mie.2018.02.022] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The enzyme soluble adenylyl cyclase (sAC) is the most recently identified source of the messenger molecule cyclic adenosine monophosphate. sAC is evolutionarily conserved from cyanobacteria to human, is directly stimulated by [Formula: see text] ions, and can act as a sensor of environmental and metabolic CO2, pH, and [Formula: see text] levels. sAC genes tend to have multiple alternative promoters, undergo extensive alternative splicing, be translated into low mRNA levels, and the numerous sAC protein isoforms may be present in various subcellular localizations. In aquatic organisms, sAC has been shown to mediate various functions including intracellular pH regulation in coral, blood acid/base regulation in shark, heart beat rate in hagfish, and NaCl absorption in fish intestine. Furthermore, sAC is present in multiple other species and tissues, and sAC protein and enzymatic activity have been reported in the cytoplasm, the nucleus, and other subcellular compartments, suggesting even more diverse physiological roles. Although the methods and experimental tools used to study sAC are conventional, the complexity of sAC genes and proteins requires special considerations that are discussed in this chapter.
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17
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Ruhr IM, Schauer KL, Takei Y, Grosell M. Renoguanylin stimulates apical CFTR translocation and decreases HCO 3- secretion through PKA activity in the Gulf toadfish ( Opsanus beta). ACTA ACUST UNITED AC 2018; 221:jeb.173948. [PMID: 29361605 DOI: 10.1242/jeb.173948] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Accepted: 01/15/2018] [Indexed: 01/07/2023]
Abstract
The guanylin peptides - guanylin, uroguanylin and renoguanylin (RGN) - are endogenously produced hormones in teleost fish enterocytes that are activators of guanylyl cyclase-C (GC-C) and are potent modulators of intestinal physiology, particularly in seawater teleosts. Most notably, they reverse normal net ion-absorbing mechanisms that are vital to water absorption, an important process for seawater teleost survival. The role of guanylin-peptide stimulation of the intestine remains unclear, but it is hypothesized to facilitate the removal of solids from the intestine by providing fluid to enable their removal by peristalsis. The present study used one member of this group of peptides - RGN - to provide evidence for the prominent role that protein kinase A (PKA) plays in mediating the effects of guanylin-peptide stimulation in the posterior intestine of the Gulf toadfish (Opsanus beta). Protein kinase G was found to not mediate the intracellular effects of RGN, despite previous evidence showing that GC-C activation leads to higher cyclic guanosine monophosphate formation. RGN reversed the absorptive short-circuit current and increased conductance in the Gulf toadfish intestine. These effects are correlated to increased trafficking of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel to the apical membrane, which is negated by PKA inhibition. Moreover, RGN decreased HCO3- secretion, likely by limiting apical HCO3-/Cl- exchange (possibly by reducing SLC26a6 activity), a reduction that was enhanced by PKA inhibition. RGN seems to alter PKA activity in the posterior intestine to recruit CFTR to the apical membrane and reduce HCO3- secretion.
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Affiliation(s)
- Ilan M Ruhr
- Department of Marine Biology and Ecology, The Rosenstiel School of Marine and Atmospheric Science, The University of Miami, Miami, FL 33149, USA
| | - Kevin L Schauer
- Department of Marine Biology and Ecology, The Rosenstiel School of Marine and Atmospheric Science, The University of Miami, Miami, FL 33149, USA
| | - Yoshio Takei
- Department of Marine Bioscience, The Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, Japan
| | - Martin Grosell
- Department of Marine Biology and Ecology, The Rosenstiel School of Marine and Atmospheric Science, The University of Miami, Miami, FL 33149, USA
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18
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Esbaugh AJ, Cutler B. Intestinal Na+, K+, 2Cl- cotransporter 2 plays a crucial role in hyperosmotic transitions of a euryhaline teleost. Physiol Rep 2017; 4:4/22/e13028. [PMID: 27881573 PMCID: PMC5358003 DOI: 10.14814/phy2.13028] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Revised: 10/06/2016] [Accepted: 10/07/2016] [Indexed: 11/29/2022] Open
Abstract
Euryhaline fishes, such as the red drum (Sciaenops ocellatus), must quickly transition between hyperosmotic and hypoosmotic physiological strategies. When freshwater individuals transition to seawater they are exposed to increased diffusive water loss and ion gain. To maintain osmoregulatory balance these animals must drink and absorb seawater through the intestine, followed by ion excretion at the gills. The ability of fishes to transition between strategies can limit the magnitude of osmotic shock that can be tolerated. Here, we demonstrate that red drum can tolerate direct transfer from freshwater to full‐strength seawater with marginal impacts on osmotic balance, as indicated by plasma and muscle ion concentration, as well as muscle water. Seawater transition is concurrent with a significant increase in intestinal fluid volume. Typical patterns of osmoregulatory plasticity were observed in the gill with increased expression of nkcc1 and cftr. Expression changes in the anterior intestine were observed after 24 h for nkcc2 with smaller and later responses observed for slc26a3, slc26a6, and nbc. Immunofluorescence staining demonstrated similar patterns of NKCC localization in freshwater and seawater intestines; however, reduced basolateral staining of V‐type ATPase was observed in seawater. Electrophysiological preparations demonstrated that seawater fish had increased absorptive current in the anterior intestine, which was significantly reduced in the presence of 10 μmol/L bumetanide. Overall, these results suggest that nkcc2 plays a crucial role during hyperosmotic transitions, and may be a more important complement to the well‐known bicarbonate secretion pathway than generally considered.
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Affiliation(s)
- Andrew J Esbaugh
- University of Texas at Austin Marine Science Institute, Austin, Texas
| | - Brett Cutler
- University of Texas at Austin Marine Science Institute, Austin, Texas
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19
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Roa JN, Tresguerres M. Bicarbonate-sensing soluble adenylyl cyclase is present in the cell cytoplasm and nucleus of multiple shark tissues. Physiol Rep 2017; 5:5/2/e13090. [PMID: 28108644 PMCID: PMC5269408 DOI: 10.14814/phy2.13090] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Accepted: 11/30/2016] [Indexed: 12/31/2022] Open
Abstract
The enzyme soluble adenylyl cyclase (sAC) is directly stimulated by bicarbonate (HCO3−) to produce the signaling molecule cyclic adenosine monophosphate (cAMP). Because sAC and sAC‐related enzymes are found throughout phyla from cyanobacteria to mammals and they regulate cell physiology in response to internal and external changes in pH, CO2, and HCO3−, sAC is deemed an evolutionarily conserved acid‐base sensor. Previously, sAC has been reported in dogfish shark and round ray gill cells, where they sense and counteract blood alkalosis by regulating the activity of V‐type H+‐ ATPase. Here, we report the presence of sAC protein in gill, rectal gland, cornea, intestine, white muscle, and heart of leopard shark Triakis semifasciata. Co‐expression of sAC with transmembrane adenylyl cyclases supports the presence of cAMP signaling microdomains. Furthermore, immunohistochemistry on tissue sections, and western blots and cAMP‐activity assays on nucleus‐enriched fractions demonstrate the presence of sAC protein in and around nuclei. These results suggest that sAC modulates multiple physiological processes in shark cells, including nuclear functions.
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Affiliation(s)
- Jinae N Roa
- Marine Biology Research Division, Scripps Institution of Oceanography University of California San Diego, 9500 Gilman Drive La Jolla, California, 92093, USA
| | - Martin Tresguerres
- Marine Biology Research Division, Scripps Institution of Oceanography University of California San Diego, 9500 Gilman Drive La Jolla, California, 92093, USA
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20
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Ruiz-Jarabo I, Barany A, Jerez-Cepa I, Mancera JM, Fuentes J. Intestinal response to salinity challenge in the Senegalese sole (Solea senegalensis). Comp Biochem Physiol A Mol Integr Physiol 2016; 204:57-64. [PMID: 27865855 DOI: 10.1016/j.cbpa.2016.11.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Revised: 09/08/2016] [Accepted: 11/14/2016] [Indexed: 12/27/2022]
Abstract
Fish are continuously forced to actively absorb or expel water and ions through epithelia. Most studies have focused on the gill due to its role in Na+ and Cl- trafficking. However, comparatively few studies have focused on the changing function of the intestine in response to external salinity. Therefore, the present study investigated the main intestinal changes of long-term acclimation of the Senegalese sole (Solea senegalensis) to 5, 15, 38 and 55ppt. Through the measurement of short-circuit current (Isc) in Ussing chambers and biochemical approaches, we described a clear anterior/posterior functional regionalization of the intestine in response to salinity. The use of specific inhibitors in Ussing chamber experiments, revealed that the bumetanide-sensitive Na+/K+/Cl- co-transporters are the main effectors of Cl- uptake in both anterior intestine and rectum. Additionally, the use of the anion exchanger specific inhibitor, DIDS, showed a salinity/region dependency of anion exchanger function. Moreover, we also described ouabain-sensitive Na+/K+-ATPase (NKA) and Bafilomycin A1-sensitive H+-ATPase activities (HA), which displayed changes related to salinity and intestinal region. However, the most striking result of the present study is the description of an omeprazole-sensitive H+/K+-ATPase (HKA) in the rectum of Senegalese sole. Its activity was consistently measurable and increased at lower salinities, reaching rates even higher than those of the NKA. Together our results provide new insights into the changing role of the intestine in response to external salinity in teleost fish. The rectal activity of HKA offers an alternative/cooperative mechanism with the HA in the final processing of intestinal water absorption by apical titration of secreted bicarbonate.
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Affiliation(s)
- I Ruiz-Jarabo
- Comparative Endocrinology and Integrative Biology, Centre of Marine Sciences (CCMar), Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal; Departamento de Biología, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, 11510, Puerto Real, Cádiz, Spain
| | - A Barany
- Comparative Endocrinology and Integrative Biology, Centre of Marine Sciences (CCMar), Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal; Departamento de Biología, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, 11510, Puerto Real, Cádiz, Spain
| | - I Jerez-Cepa
- Departamento de Biología, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, 11510, Puerto Real, Cádiz, Spain
| | - J M Mancera
- Departamento de Biología, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, 11510, Puerto Real, Cádiz, Spain
| | - J Fuentes
- Comparative Endocrinology and Integrative Biology, Centre of Marine Sciences (CCMar), Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal.
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21
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Wilson CM, Roa JN, Cox GK, Tresguerres M, Farrell AP. Introducing a novel mechanism to control heart rate in the ancestral Pacific hagfish. ACTA ACUST UNITED AC 2016; 219:3227-3236. [PMID: 27510962 DOI: 10.1242/jeb.138198] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Accepted: 08/02/2016] [Indexed: 12/15/2022]
Abstract
Although neural modulation of heart rate is well established among chordate animals, the Pacific hagfish (Eptatretus stoutii) lacks any cardiac innervation, yet it can increase its heart rate from the steady, depressed heart rate seen in prolonged anoxia to almost double its normal normoxic heart rate, an almost fourfold overall change during the 1-h recovery from anoxia. The present study sought mechanistic explanations for these regulatory changes in heart rate. We provide evidence for a bicarbonate-activated, soluble adenylyl cyclase (sAC)-dependent mechanism to control heart rate, a mechanism never previously implicated in chordate cardiac control.
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Affiliation(s)
- Christopher M Wilson
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, British Columbia, Canada V6T 1Z4
| | - Jinae N Roa
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Georgina K Cox
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, British Columbia, Canada V6T 1Z4
| | - Martin Tresguerres
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Anthony P Farrell
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, British Columbia, Canada V6T 1Z4.,Faculty of Land and Food Systems, University of British Columbia, 2357 Main Mall, Vancouver, British Columbia, Canada V6T 1Z4
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22
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Roa JN, Tresguerres M. Soluble adenylyl cyclase is an acid-base sensor in epithelial base-secreting cells. Am J Physiol Cell Physiol 2016; 311:C340-9. [PMID: 27335168 DOI: 10.1152/ajpcell.00089.2016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 06/16/2016] [Indexed: 12/20/2022]
Abstract
Blood acid-base regulation by specialized epithelia, such as gills and kidney, requires the ability to sense blood acid-base status. Here, we developed primary cultures of ray (Urolophus halleri) gill cells to study mechanisms for acid-base sensing without the interference of whole animal hormonal regulation. Ray gills have abundant base-secreting cells, identified by their noticeable expression of vacuolar-type H(+)-ATPase (VHA), and also express the evolutionarily conserved acid-base sensor soluble adenylyl cyclase (sAC). Exposure of cultured cells to extracellular alkalosis (pH 8.0, 40 mM HCO3 (-)) triggered VHA translocation to the cell membrane, similar to previous reports in live animals experiencing blood alkalosis. VHA translocation was dependent on sAC, as it was blocked by the sAC-specific inhibitor KH7. Ray gill base-secreting cells also express transmembrane adenylyl cyclases (tmACs); however, tmAC inhibition by 2',5'-dideoxyadenosine did not prevent alkalosis-dependent VHA translocation, and tmAC activation by forskolin reduced the abundance of VHA at the cell membrane. This study demonstrates that sAC is a necessary and sufficient sensor of extracellular alkalosis in ray gill base-secreting cells. In addition, this study indicates that different sources of cAMP differentially modulate cell biology.
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Affiliation(s)
- Jinae N Roa
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California
| | - Martin Tresguerres
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California
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23
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Hu MY, Michael K, Kreiss CM, Stumpp M, Dupont S, Tseng YC, Lucassen M. Temperature Modulates the Effects of Ocean Acidification on Intestinal Ion Transport in Atlantic Cod, Gadus morhua. Front Physiol 2016; 7:198. [PMID: 27313538 PMCID: PMC4889603 DOI: 10.3389/fphys.2016.00198] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2016] [Accepted: 05/17/2016] [Indexed: 01/09/2023] Open
Abstract
CO2-driven seawater acidification has been demonstrated to enhance intestinal bicarbonate secretion rates in teleosts, leading to an increased release of CaCO3 under simulated ocean acidification scenarios. In this study, we investigated if increasing CO2 levels stimulate the intestinal acid–base regulatory machinery of Atlantic cod (Gadus morhua) and whether temperatures at the upper limit of thermal tolerance stimulate or counteract ion regulatory capacities. Juvenile G. morhua were acclimated for 4 weeks to three CO2 levels (550, 1200, and 2200 μatm) covering present and near-future natural variability, at optimum (10°C) and summer maximum temperature (18°C), respectively. Immunohistochemical analyses revealed the subcellular localization of ion transporters, including Na+/K+-ATPase (NKA), Na+/H+-exchanger 3 (NHE3), Na+/HCO3− cotransporter (NBC1), pendrin-like Cl−/HCO3− exchanger (SLC26a6), V-type H+-ATPase subunit a (VHA), and Cl− channel 3 (CLC3) in epithelial cells of the anterior intestine. At 10°C, proteins and mRNA were generally up-regulated for most transporters in the intestinal epithelium after acclimation to higher CO2 levels. This supports recent findings demonstrating increased intestinal HCO3− secretion rates in response to CO2 induced seawater acidification. At 18°C, mRNA expression and protein concentrations of most ion transporters remained unchanged or were even decreased, suggesting thermal compensation. This response may be energetically favorable to retain blood HCO3− levels to stabilize pHe, but may negatively affect intestinal salt and water resorption of marine teleosts in future oceans.
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Affiliation(s)
- Marian Y Hu
- Institute of Physiology, University of Kiel Kiel, Germany
| | - Katharina Michael
- Helmholtz Center for Polar and Marine Research, Alfred Wegener Institute Bremerhaven, Germany
| | - Cornelia M Kreiss
- Helmholtz Center for Polar and Marine Research, Alfred Wegener Institute Bremerhaven, Germany
| | - Meike Stumpp
- Helmholtz Centre for Ocean Research Kiel Kiel, Germany
| | - Sam Dupont
- Department of Biological and Environmental Sciences, The Sven Lovén Centre for Marine Sciences, University of Gothenburg Gothenburg, Sweden
| | - Yung-Che Tseng
- Department of Life Science, National Taiwan Normal University Taipei City, Taiwan
| | - Magnus Lucassen
- Helmholtz Center for Polar and Marine Research, Alfred Wegener Institute Bremerhaven, Germany
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Ruhr IM, Mager EM, Takei Y, Grosell M. The differential role of renoguanylin in osmoregulation and apical Cl−/HCO3− exchange activity in the posterior intestine of the Gulf toadfish (Opsanus beta). Am J Physiol Regul Integr Comp Physiol 2015; 309:R399-409. [DOI: 10.1152/ajpregu.00118.2015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Accepted: 05/20/2015] [Indexed: 11/22/2022]
Abstract
The guanylin family of peptides are effective regulators of intestinal physiology in marine teleosts. In the distal intestinal segments, they inhibit or reverse fluid absorption by inhibiting the absorptive short-circuit current ( Isc). The present findings demonstrate that mRNA from guanylin and uroguanylin, as well as at least one isoform of the guanylin peptide receptor, apical guanylyl cyclase-C (GC-C), was highly expressed in the intestine and rectum of the Gulf toadfish ( Opsanus beta). In the posterior intestine, GC-C, as well as the cystic fibrosis transmembrane conductance regulator and basolateral Na+/K+/2Cl− cotransporter, which comprise a Cl−-secretory pathway, were transcriptionally upregulated in 60 parts per thousand (ppt). The present study also shows that, in intestinal tissues from Gulf toadfish held in 35 ppt, renoguanylin (RGN) expectedly causes net Cl− secretion, inhibits both the absorptive Isc and fluid absorption, and decreases HCO3− secretion. Likewise, in intestinal tissues from Gulf toadfish acclimated to 60 ppt, RGN also inhibits the absorptive Isc and fluid absorption but to an even greater extent, corresponding with the mRNA expression data. In contrast, RGN does not alter Cl− flux and, instead, elevates HCO3− secretion in the 60-ppt group, suggesting increased apical Cl−/HCO3− exchange activity by SLC26a6. Overall, these findings reinforce the hypotheses that the guanylin peptide system is important for salinity acclimatization and that the secretory response could facilitate the removal of solids, such as CaCO3 precipitates, from the intestine.
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Affiliation(s)
- Ilan M. Ruhr
- Department of Marine Biology and Ecology, The Rosenstiel School of Marine and Atmospheric Science, The University of Miami, Miami, Florida
| | - Edward M. Mager
- Department of Marine Biology and Ecology, The Rosenstiel School of Marine and Atmospheric Science, The University of Miami, Miami, Florida
| | - Yoshio Takei
- Department of Marine Bioscience, The Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, Japan
| | - Martin Grosell
- Department of Marine Biology and Ecology, The Rosenstiel School of Marine and Atmospheric Science, The University of Miami, Miami, Florida
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Carvalho ESM, Gregório SF, Canário AVM, Power DM, Fuentes J. PTHrP regulates water absorption and aquaporin expression in the intestine of the marine sea bream (Sparus aurata, L.). Gen Comp Endocrinol 2015; 213:24-31. [PMID: 25562629 DOI: 10.1016/j.ygcen.2014.12.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Revised: 12/25/2014] [Accepted: 12/27/2014] [Indexed: 11/22/2022]
Abstract
Water ingestion by drinking is fundamental for ion homeostasis in marine fish. However, the fluid ingested requires processing to allow net water absorption in the intestine. The formation of luminal carbonate aggregates impacts on calcium homeostasis and requires epithelial HCO3(-) secretion to enable water absorption. In light of its endocrine importance in calcium handling and the indication of involvement in HCO3(-) secretion the present study was designed to expose the role of the parathyroid hormone-related protein (PTHrP) in HCO3(-) secretion, water absorption and the regulation of aqp1 gene expression in the anterior intestine of the sea bream. HCO3(-) secretion rapidly decreased when PTHrP(1-34) was added to anterior intestine of the sea bream mounted in Ussing chambers. The effect achieved a maximum inhibition of 60% of basal secretion rates, showing a threshold effective dose of 0.1 ng ml(-1) compatible with reported plasma values of PTHrP. When applied in combination with the adenylate cyclase inhibitor (SQ 22.536, 100 μmol l(-1)) or the phospholipase C inhibitor (U73122, 10 μmol l(-1)) the effect of PTHrP(1-34) on HCO3(-) secretion was reduced by about 50% in both cases. In parallel, bulk water absorption measured in intestinal sacs was sensitive to inhibition by PTHrP. The inhibitory action conforms to a typical dose-response curve in the range of 0.1-1000 ng ml(-1), achieves a maximal effect of 60-65% inhibition from basal rates and shows threshold significant effects at hormone levels of 0.1 ng ml(-1). The action of PTHrP in water absorption was completely abolished in the presence of the adenylate cyclase inhibitor (SQ 22.536, 100 μmol l(-1)) and was insensitive to the phospholipase C inhibitor (U73122, 10 μmol l(-1)). In vivo injections of PTHrP(1-34) or the PTH/PTHrP receptor antagonist PTHrP(7-34) evoked respectively, a significant decrease or increase of aqp1ab, but not aqp1a. Overall the present results suggest that PTHrP acts as a key regulator of carbonate aggregate formation in the intestine of marine fish via its actions on water absorption, calcium regulation and HCO3(-) secretion.
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Affiliation(s)
- Edison S M Carvalho
- Centre of Marine Sciences (CCMar), Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal
| | - Sílvia F Gregório
- Centre of Marine Sciences (CCMar), Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal
| | - Adelino V M Canário
- Centre of Marine Sciences (CCMar), Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal
| | - Deborah M Power
- Centre of Marine Sciences (CCMar), Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal
| | - Juan Fuentes
- Centre of Marine Sciences (CCMar), Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal.
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Rubino JG, Zimmer AM, Wood CM. Intestinal ammonia transport in freshwater and seawater acclimated rainbow trout (Oncorhynchus mykiss): evidence for a Na+ coupled uptake mechanism. Comp Biochem Physiol A Mol Integr Physiol 2014; 183:45-56. [PMID: 25545914 DOI: 10.1016/j.cbpa.2014.12.037] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2014] [Revised: 12/17/2014] [Accepted: 12/19/2014] [Indexed: 12/23/2022]
Abstract
In vitro gut sac experiments were performed on freshwater and 60% seawater acclimated trout (Oncorhynchus mykiss) under treatments designed to discern possible mechanisms of intestinal ammonia transport. Seawater acclimation increased ammonia flux rate into the serosal saline (Jsamm) in the anterior intestine, however it did not alter Jsamm in the mid- or posterior intestine suggesting similar mechanisms of ammonia handling in freshwater and seawater fish. Both fluid transport rate (FTR) and Jsamm were inhibited in response to basolateral ouabain treatment, suggesting a linkage of ammonia uptake to active transport, possibly coupled to fluid transport processes via solvent drag. Furthermore, decreases in FTR and Jsamm caused by low Na(+) treatment indicated a Na(+) linked transport mechanism. Mucosal bumetanide (10(-4) M) had no impact on FTR, yet decreased Jsamm in the anterior and mid-intestine, suggesting NH4(+) substitution for K(+) on an apical NKCC, and at least a partial uncoupling of ammonia transport from fluid transport. Additional treatments (amiloride, 5-(N-ethyl-N-isopropyl)amiloride (EIPA), phenamil, bafilomycin, 4',6-diamidino-2-phenylindole (DAPI), high sodium) intended to disrupt alternative routes of Na(+) uptake yielded no change in FTR or Jsamm, suggesting the absence of direct competition between Na(+) and ammonia for transport. Finally, [(14)C]methylamine permeability (PMA) measurements indicated the likely presence of an intestinal Rh-mediated ammonia transport system, as increasing NH4Cl (0, 1, 5 mmol l(-1)) concentrations reduced PMA, suggesting competition for transport through Rh proteins. Overall, the data presented in this paper provide some of the first insights into mechanisms of teleost intestinal ammonia transport.
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Affiliation(s)
- Julian G Rubino
- McMaster University, Life Sciences Building, Department of Biology, Hamilton, Ontario L8S 4K1, Canada; Bamfield Marine Sciences Centre, Bamfield, British Columbia V0R 1B0, Canada.
| | - Alex M Zimmer
- McMaster University, Life Sciences Building, Department of Biology, Hamilton, Ontario L8S 4K1, Canada; Bamfield Marine Sciences Centre, Bamfield, British Columbia V0R 1B0, Canada
| | - Chris M Wood
- McMaster University, Life Sciences Building, Department of Biology, Hamilton, Ontario L8S 4K1, Canada; Bamfield Marine Sciences Centre, Bamfield, British Columbia V0R 1B0, Canada; Dept. of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
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Tresguerres M, Barott KL, Barron ME, Roa JN. Established and potential physiological roles of bicarbonate-sensing soluble adenylyl cyclase (sAC) in aquatic animals. ACTA ACUST UNITED AC 2014; 217:663-72. [PMID: 24574382 DOI: 10.1242/jeb.086157] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Soluble adenylyl cyclase (sAC) is a recently recognized source of the signaling molecule cyclic AMP (cAMP) that is genetically and biochemically distinct from the classic G-protein-regulated transmembrane adenylyl cyclases (tmACs). Mammalian sAC is distributed throughout the cytoplasm and it may be present in the nucleus and inside mitochondria. sAC activity is directly stimulated by HCO3(-), and sAC has been confirmed to be a HCO3(-) sensor in a variety of mammalian cell types. In addition, sAC can functionally associate with carbonic anhydrases to act as a de facto sensor of pH and CO2. The two catalytic domains of sAC are related to HCO3(-)-regulated adenylyl cyclases from cyanobacteria, suggesting the cAMP pathway is an evolutionarily conserved mechanism for sensing CO2 levels and/or acid/base conditions. Reports of sAC in aquatic animals are still limited but are rapidly accumulating. In shark gills, sAC senses blood alkalosis and triggers compensatory H(+) absorption. In the intestine of bony fishes, sAC modulates NaCl and water absorption. And in sea urchin sperm, sAC may participate in the initiation of flagellar movement and in the acrosome reaction. Bioinformatics and RT-PCR results reveal that sAC orthologs are present in most animal phyla. This review summarizes the current knowledge on the physiological roles of sAC in aquatic animals and suggests additional functions in which sAC may be involved.
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Affiliation(s)
- Martin Tresguerres
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
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Heuer RM, Grosell M. Physiological impacts of elevated carbon dioxide and ocean acidification on fish. Am J Physiol Regul Integr Comp Physiol 2014; 307:R1061-84. [DOI: 10.1152/ajpregu.00064.2014] [Citation(s) in RCA: 258] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Most fish studied to date efficiently compensate for a hypercapnic acid-base disturbance; however, many recent studies examining the effects of ocean acidification on fish have documented impacts at CO2 levels predicted to occur before the end of this century. Notable impacts on neurosensory and behavioral endpoints, otolith growth, mitochondrial function, and metabolic rate demonstrate an unexpected sensitivity to current-day and near-future CO2 levels. Most explanations for these effects seem to center on increases in Pco2 and HCO3− that occur in the body during pH compensation for acid-base balance; however, few studies have measured these parameters at environmentally relevant CO2 levels or directly related them to reported negative endpoints. This compensatory response is well documented, but noted variation in dynamic regulation of acid-base transport pathways across species, exposure levels, and exposure duration suggests that multiple strategies may be utilized to cope with hypercapnia. Understanding this regulation and changes in ion gradients in extracellular and intracellular compartments during CO2 exposure could provide a basis for predicting sensitivity and explaining interspecies variation. Based on analysis of the existing literature, the present review presents a clear message that ocean acidification may cause significant effects on fish across multiple physiological systems, suggesting that pH compensation does not necessarily confer tolerance as downstream consequences and tradeoffs occur. It remains difficult to assess if acclimation responses during abrupt CO2 exposures will translate to fitness impacts over longer timescales. Nonetheless, identifying mechanisms and processes that may be subject to selective pressure could be one of many important components of assessing adaptive capacity.
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Affiliation(s)
- Rachael M. Heuer
- Rosenstiel School of Marine and Atmospheric Science, University of Miami, Marine Biology and Fisheries, Miami, Florida
| | - Martin Grosell
- Rosenstiel School of Marine and Atmospheric Science, University of Miami, Marine Biology and Fisheries, Miami, Florida
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Ruhr IM, Bodinier C, Mager EM, Esbaugh AJ, Williams C, Takei Y, Grosell M. Guanylin peptides regulate electrolyte and fluid transport in the Gulf toadfish (Opsanus beta) posterior intestine. Am J Physiol Regul Integr Comp Physiol 2014; 307:R1167-79. [DOI: 10.1152/ajpregu.00188.2014] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The physiological effects of guanylin (GN) and uroguanylin (UGN) on fluid and electrolyte transport in the teleost fish intestine have yet to be thoroughly investigated. In the present study, the effects of GN, UGN, and renoguanylin (RGN; a GN and UGN homolog) on short-circuit current ( Isc) and the transport of Cl−, Na+, bicarbonate (HCO3−), and fluid in the Gulf toadfish ( Opsanus beta) intestine were determined using Ussing chambers, pH-stat titration, and intestinal sac experiments. GN, UGN, and RGN reversed the Isc of the posterior intestine (absorptive-to-secretory), but not of the anterior intestine. RGN decreased baseline HCO3− secretion, but increased Cl− and fluid secretion in the posterior intestine. The secretory response of the posterior intestine coincides with the presence of basolateral NKCC1 and apical cystic fibrosis transmembrane conductance regulator (CFTR), the latter of which is lacking in the anterior intestine and is not permeable to HCO3− in the posterior intestine. However, the response to RGN by the posterior intestine is counterintuitive given the known role of the marine teleost intestine as a salt- and water-absorbing organ. These data demonstrate that marine teleosts possess a tissue-specific secretory response, apparently associated with seawater adaptation, the exact role of which remains to be determined.
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Affiliation(s)
- Ilan M. Ruhr
- Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida; and
| | - Charlotte Bodinier
- Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida; and
| | - Edward M. Mager
- Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida; and
| | - Andrew J. Esbaugh
- Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida; and
| | - Cameron Williams
- Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida; and
| | - Yoshio Takei
- Ocean Research Institute, University of Tokyo, Tokyo, Japan
| | - Martin Grosell
- Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida; and
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Tresguerres M. sAC from aquatic organisms as a model to study the evolution of acid/base sensing. Biochim Biophys Acta Mol Basis Dis 2014; 1842:2629-35. [PMID: 24971688 DOI: 10.1016/j.bbadis.2014.06.021] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Accepted: 06/17/2014] [Indexed: 12/26/2022]
Abstract
Soluble adenylyl cyclase (sAC) is poised to play multiple physiological roles as an acid/base (A/B) sensor in aquatic organisms. Many of these roles are probably similar to those in mammals; a striking example is the evolutionary conservation of a mechanism involving sAC, carbonic anhydrase and vacuolar H⁺-ATPase that acts as a sensor system and regulator of extracellular A/B in shark gills and mammalian epididymis and kidney. Additionally, the aquatic environment presents unique A/B and physiological challenges; therefore, sACs from aquatic organisms have likely evolved distinct kinetic properties as well as distinct physiological roles. sACs from aquatic organisms offer an excellent opportunity for studying the evolution of A/B sensing at both the molecular and whole organism levels. Moreover, this information could help understand and predict organismal responses to environmental stress based on mechanistic models.This article is part of a Special Issue entitled "The Role of Soluble Adenylyl Cyclase in Health and Disease," guest edited by J. Buck and L. R. Levin.
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Affiliation(s)
- Martin Tresguerres
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA.
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31
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Larsen EH, Deaton LE, Onken H, O'Donnell M, Grosell M, Dantzler WH, Weihrauch D. Osmoregulation and Excretion. Compr Physiol 2014; 4:405-573. [DOI: 10.1002/cphy.c130004] [Citation(s) in RCA: 127] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Sabbatini ME, Gorelick F, Glaser S. Adenylyl cyclases in the digestive system. Cell Signal 2014; 26:1173-81. [PMID: 24521753 DOI: 10.1016/j.cellsig.2014.01.033] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2014] [Accepted: 01/31/2014] [Indexed: 02/08/2023]
Abstract
Adenylyl cyclases (ACs) are a group of widely distributed enzymes whose functions are very diverse. There are nine known transmembrane AC isoforms activated by Gαs. Each has its own pattern of expression in the digestive system and differential regulation of function by Ca(2+) and other intracellular signals. In addition to the transmembrane isoforms, one AC is soluble and exhibits distinct regulation. In this review, the basic structure, regulation and physiological roles of ACs in the digestive system are discussed.
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Affiliation(s)
| | - Fred Gorelick
- Department of Cell Biology and Medicine, Yale University, United States; VA CT, United States
| | - Shannon Glaser
- Department of Internal Medicine, Scott & White-Digestive Disease Research Center, Texas A&M Health Science Center, Central Texas Veterans Health Care System, United States
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33
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Kumai Y, Kwong RWM, Perry SF. The role of cAMP-mediated intracellular signaling in regulating Na+ uptake in zebrafish larvae. Am J Physiol Regul Integr Comp Physiol 2013; 306:R51-60. [PMID: 24259461 DOI: 10.1152/ajpregu.00317.2013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the current study, the role of cAMP in stimulating Na(+) uptake in larval zebrafish was investigated. Treating larvae at 4 days postfertilization (dpf) with 10 μM forskolin or 1 μM 8-bromo cAMP significantly increased Na(+) uptake by three-fold and twofold, respectively. The cAMP-dependent stimulation of Na(+) uptake was probably unrelated to protein trafficking via microtubules because pretreatment with 200 μM colchicine or 30 μM nocodazole did not attenuate the magnitude of the response. Na(+) uptake was stimulated markedly following acute (2 h) exposure to acidic water. The acid-induced increase in Na(+) uptake was accompanied by a twofold elevation in whole body cAMP levels and attenuated by inhibiting PKA with 10 μM H-89. Knockdown of Na(+)-H(+) exchanger 3b (NHE3b) attenuated, but did not abolish, the stimulation of Na(+) uptake during forskolin treatment. In glial cell missing 2 morphants, in which the role of NHE3b in Na(+) uptake is diminished and the Na(+)-Cl(-) cotransporter (NCC) becomes the predominant route of Na(+) entry, forskolin treatment continued to increase Na(+) uptake. These data suggest that at least NHE3b and NCC are targeted by cAMP in zebrafish larvae. Staining of larvae with fluorescent forskolin and propranolol revealed the presence of transmembrane adenylyl cyclase within multiple subtypes of ionocytes expressing β-adrenergic receptors. Taken together, results of the present study demonstrate that cAMP-mediated intracellular signaling may regulate multiple Na(+) transporters and plays an important role in regulating Na(+) uptake in zebrafish larvae during acute exposure to an acidic environment.
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Affiliation(s)
- Yusuke Kumai
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
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Barott KL, Helman Y, Haramaty L, Barron ME, Hess KC, Buck J, Levin LR, Tresguerres M. High adenylyl cyclase activity and in vivo cAMP fluctuations in corals suggest central physiological role. Sci Rep 2013; 3:1379. [PMID: 23459251 PMCID: PMC3587883 DOI: 10.1038/srep01379] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2012] [Accepted: 02/20/2013] [Indexed: 11/29/2022] Open
Abstract
Corals are an ecologically and evolutionarily significant group, providing the framework for coral reef biodiversity while representing one of the most basal of metazoan phyla. However, little is known about fundamental signaling pathways in corals. Here we investigate the dynamics of cAMP, a conserved signaling molecule that can regulate virtually every physiological process. Bioinformatics revealed corals have both transmembrane and soluble adenylyl cyclases (AC). Endogenous cAMP levels in live corals followed a potential diel cycle, as they were higher during the day compared to the middle of the night. Coral homogenates exhibited some of the highest cAMP production rates ever to be recorded in any organism; this activity was inhibited by calcium ions and stimulated by bicarbonate. In contrast, zooxanthellae or mucus had >1000-fold lower AC activity. These results suggest that cAMP is an important regulator of coral physiology, especially in response to light, acid/base disturbances and inorganic carbon levels.
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Affiliation(s)
- K. L. Barott
- Scripps Institution of Oceanography, Marine Biology Research Division, La Jolla, California, United States of America
| | - Y. Helman
- Environmental Biophysics and Molecular Ecology Program, Institute of Marine and Coastal Sciences, Rutgers, State University of New Jersey, New Brunswick, New Jersey, United States of America
- Current address: Department of Plant Pathology and Microbiology, Hebrew University of Jerusalem, Israel
| | - L. Haramaty
- Environmental Biophysics and Molecular Ecology Program, Institute of Marine and Coastal Sciences, Rutgers, State University of New Jersey, New Brunswick, New Jersey, United States of America
| | - M. E. Barron
- Scripps Institution of Oceanography, Marine Biology Research Division, La Jolla, California, United States of America
| | - K. C. Hess
- Weill Cornell Medical College, Department of Pharmacology, New York City, New York, United States of America
| | - J. Buck
- Weill Cornell Medical College, Department of Pharmacology, New York City, New York, United States of America
| | - L. R. Levin
- Weill Cornell Medical College, Department of Pharmacology, New York City, New York, United States of America
| | - M. Tresguerres
- Scripps Institution of Oceanography, Marine Biology Research Division, La Jolla, California, United States of America
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Sundell KS, Sundh H. Intestinal fluid absorption in anadromous salmonids: importance of tight junctions and aquaporins. Front Physiol 2012; 3:388. [PMID: 23060812 PMCID: PMC3460234 DOI: 10.3389/fphys.2012.00388] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Accepted: 09/11/2012] [Indexed: 01/17/2023] Open
Abstract
The anadromous salmonid life cycle includes both fresh water (FW) and seawater (SW) stages. The parr-smolt transformation (smoltification) pre-adapt the fish to SW while still in FW. The osmoregulatory organs change their mode of action from a role of preventing water inflow in FW, to absorb ions to replace water lost by osmosis in SW. During smoltification, the drinking rate increases, in the intestine the ion and fluid transport increases and is further elevated after SW entry. In SW, the intestine absorbs ions to create an inwardly directed water flow which is accomplished by increased Na+, K+-ATPase (NKA) activity in the basolateral membrane, driving ion absorption via ion channels and/or co-transporters. This review will aim at discussing the expression patterns of the ion transporting proteins involved in intestinal fluid absorption in the FW stage, during smoltification and after SW entry. Of equal importance for intestinal fluid absorption as the active absorption of ions is the permeability of the epithelium to ions and water. During the smoltification the increase in NKA activity and water uptake in SW is accompanied by decreased paracellular permeability suggesting a redirection of the fluid movement from a paracellular route in FW, to a transcellular route in SW. Increased transcellular fluid absorption could be achieved by incorporation of aquaporins (AQPs) into the enterocyte membranes and/or by a change in fatty acid profile of the enterocyte lipid bilayer. An increased incorporation of unsaturated fatty acids into the membrane phospholipids will increase water permeability by enhancing the fluidity of the membrane. A second aim of the present review is therefore to discuss the presence and regulation of expression of AQPs in the enterocyte membrane as well as to discuss the profile of fatty acids present in the membrane phospholipids during different stages of the salmonid lifecycle.
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Affiliation(s)
- Kristina S Sundell
- Fish Endocrinology Laboratory, Department of Biology and Environmental Sciences, University of Gothenburg Gothenburg, Sweden
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36
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Carvalho ESM, Gregório SF, Power DM, Canário AVM, Fuentes J. Water absorption and bicarbonate secretion in the intestine of the sea bream are regulated by transmembrane and soluble adenylyl cyclase stimulation. J Comp Physiol B 2012; 182:1069-80. [PMID: 22752677 DOI: 10.1007/s00360-012-0685-4] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Revised: 06/04/2012] [Accepted: 06/09/2012] [Indexed: 10/28/2022]
Abstract
In the marine fish intestine luminal, HCO₃⁻ can remove divalent ions (calcium and magnesium) by precipitation in the form of carbonate aggregates. The process of epithelial HCO₃⁻ secretion is under endocrine control, therefore, in this study we aimed to characterize the involvement of transmembrane (tmACs) and soluble (sACs) adenylyl cyclases on the regulation of bicarbonate secretion (BCS) and water absorption in the intestine of the sea bream (Sparus aurata). We observed that all sections of sea bream intestine are able to secrete bicarbonate as measured by pH-Stat in Ussing chambers. In addition, gut sac preparations reveal net water absorption in all segments of the intestine, with significantly higher absorption rates in the anterior intestine that in the rectum. BCS and water absorption are positively correlated in all regions of the sea bream intestinal tract. Furthermore, stimulation of tmACs (10 μM FK + 500 μM IBMX) causes a significant decrease in BCS, bulk water absorption and short circuit current (Isc) in a region dependent manner. In turn, stimulation of sACs with elevated HCO₃⁻ results in a significant increase in BCS, and bulk water absorption in the anterior intestine, an action completely reversed by the sAC inhibitor KH7 (200 μM). Overall, the results reveal a functional relationship between BCS and water absorption in marine fish intestine and modulation by tmACs and sAC. In light of the present observations, it is hypothesized that the endocrine effects on intestinal BCS and water absorption mediated by tmACs are locally and reciprocally modulated by the action of sACs in the fish enterocyte, thus fine-tuning the process of carbonate aggregate production in the intestinal lumen.
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Affiliation(s)
- Edison S M Carvalho
- Centre of Marine Sciences (CCMar), CIMAR-Laboratório Associado, Universidade do Algarve, Faro, Portugal
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37
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Characterization of Plasmodium falciparum adenylyl cyclase-β and its role in erythrocytic stage parasites. PLoS One 2012; 7:e39769. [PMID: 22761895 PMCID: PMC3383692 DOI: 10.1371/journal.pone.0039769] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Accepted: 05/30/2012] [Indexed: 11/19/2022] Open
Abstract
The most severe form of human malaria is caused by the parasite Plasmodium falciparum. The second messenger cAMP has been shown to be important for the parasite's ability to infect the host's liver, but its role during parasite growth inside erythrocytes, the stage responsible for symptomatic malaria, is less clear. The P. falciparum genome encodes two adenylyl cyclases, the enzymes that synthesize cAMP, PfACα and PfACβ. We now show that one of these, PfACβ, plays an important role during the erythrocytic stage of the P. falciparum life cycle. Biochemical characterization of PfACβ revealed a marked pH dependence, and sensitivity to a number of small molecule inhibitors. These inhibitors kill parasites growing inside red blood cells. One particular inhibitor is selective for PfACβ relative to its human ortholog, soluble adenylyl cyclase (sAC); thus, PfACβ represents a potential target for development of safe and effective antimalarial therapeutics.
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Buck J, Levin LR. Physiological sensing of carbon dioxide/bicarbonate/pH via cyclic nucleotide signaling. SENSORS 2012; 11:2112-28. [PMID: 21544217 PMCID: PMC3085406 DOI: 10.3390/s110202112] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Carbon dioxide (CO2) is produced by living organisms as a byproduct of metabolism. In physiological systems, CO2 is unequivocally linked with bicarbonate (HCO3−) and pH via a ubiquitous family of carbonic anhydrases, and numerous biological processes are dependent upon a mechanism for sensing the level of CO2, HCO3, and/or pH. The discovery that soluble adenylyl cyclase (sAC) is directly regulated by bicarbonate provided a link between CO2/HCO3/pH chemosensing and signaling via the widely used second messenger cyclic AMP. This review summarizes the evidence that bicarbonate-regulated sAC, and additional, subsequently identified bicarbonate-regulate nucleotidyl cyclases, function as evolutionarily conserved CO2/HCO3/pH chemosensors in a wide variety of physiological systems.
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Affiliation(s)
- Jochen Buck
- Department of Pharmacology, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10065, USA.
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Brown D, Wagner CA. Molecular mechanisms of acid-base sensing by the kidney. J Am Soc Nephrol 2012; 23:774-80. [PMID: 22362904 DOI: 10.1681/asn.2012010029] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
A major function of the kidney is to collaborate with the respiratory system to maintain systemic acid-base status within limits compatible with normal cell and organ function. It achieves this by regulating the excretion and recovery of bicarbonate (mainly in the proximal tubule) and the secretion of buffered protons (mainly in the distal tubule and collecting duct). How proximal tubular cells and distal professional proton transporting (intercalated) cells sense and respond to changes in pH, bicarbonate, and CO(2) status is a question that has intrigued many generations of renal physiologists. Over the past few years, however, some candidate molecular pH sensors have been identified, including acid/alkali-sensing receptors (GPR4, InsR-RR), kinases (Pyk2, ErbB1/2), pH-sensitive ion channels (ASICs, TASK, ROMK), and the bicarbonate-stimulated adenylyl cyclase (sAC). Some acid-sensing mechanisms in other tissues, such as CAII-PDK2L1 in taste buds, might also have similar roles to play in the kidney. Finally, the function of a variety of additional membrane channels and transporters is altered by pH variations both within and outside the cell, and the expression of several metabolic enzymes are altered by acid-base status in parts of the nephron. Thus, it is possible that a master pH sensor will never be identified. Rather, the kidney seems equipped with a battery of molecules that scan the epithelial cell environment to mount a coordinated physiologic response that maintains acid-base homeostasis. This review collates current knowledge on renal acid-base sensing in the context of a whole organ sensing and response process.
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Affiliation(s)
- Dennis Brown
- MGH Center for Systems Biology, Program in Membrane Biology, Boston, MA, USA.
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Al-Jandal NJ, Whittamore JM, Santos EM, Wilson RW. The influence of 17β-estradiol on intestinal calcium carbonate precipitation and osmoregulation in seawater-acclimated rainbow trout (Oncorhynchus mykiss). ACTA ACUST UNITED AC 2011; 214:2791-8. [PMID: 21795578 DOI: 10.1242/jeb.054296] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The intestine of marine teleosts produces carbonate precipitates from ingested calcium as part of their osmoregulatory strategy in seawater. The potential for estrogens to control the production of intestinal calcium carbonate and so influence osmoregulation was investigated in seawater-acclimated rainbow trout following intraperitoneal implantation of 17β-estradiol (E2) at two doses (0.1 and 10 μg E2 g(-1)). Levels of plasma vitellogenin provided an indicator of estrogenic effect, increasing significantly by three and four orders of magnitude at the low and high doses, respectively. Plasma osmolality and muscle water content were unaffected, whereas E2-treated fish maintained lower plasma [Na(+)] and [Cl(-)]. Plasma [Ca(2+)] and [Mg(2+)] and muscle [Ca(2+)] increased with vitellogenin induction, whereas the intestinal excretion of calcium carbonate was reduced. This suggests that elevated levels of circulating E2 may enhance Ca(2+) uptake via the gut and simultaneously reduce CaCO(3) formation, which normally limits intestinal availability of Ca(2+). Increasing E2 caused an elevation of [Na(+)] and [Cl(-)] and a reduction of [HCO(3(-))] in intestinal fluid. We speculate that E2 may influence a number of intestinal ion transport processes that ultimately may influence water absorption: (1) reduced NaCl cotransport, (2) reduced Cl(-) uptake via Cl(-)/HCO(3(-)) exchange and (3) reduced precipitation of Ca(2+) and Mg(2+) carbonates. Despite these effects on intestinal ion and water transport, overall osmoregulatory status was not compromised in E2-treated fish, suggesting the possibility of compensation by other organs.
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Affiliation(s)
- Noura J Al-Jandal
- Biosciences, College of Life and Environmental Sciences, Hatherly Laboratories, University of Exeter, Exeter EX4 4PS, UK
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Guffey S, Esbaugh A, Grosell M. Regulation of apical H⁺-ATPase activity and intestinal HCO₃⁻ secretion in marine fish osmoregulation. Am J Physiol Regul Integr Comp Physiol 2011; 301:R1682-91. [PMID: 21865541 DOI: 10.1152/ajpregu.00059.2011] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The absorption of Cl(-) and water from ingested seawater in the marine fish intestine is accomplished partly through Cl(-)/HCO(3)(-) exchange. Recently, a H(+) pump (vacuolar-type H(+)-ATPase) was found to secrete acid into the intestinal lumen, and it may serve to titrate luminal HCO(3)(-) and facilitate further Cl(-)/HCO(3)(-) exchange, especially in the posterior intestine, where adverse concentration gradients could limit Cl(-)/HCO(3)(-) exchange. The H(+) pump is expressed in all intestinal segments and in gill tissue of gulf toadfish (Opsanus beta) maintained in natural seawater. After acute transfer of toadfish to 60 ppt salinity, H(+) pump expression increased 20-fold in the posterior intestine. In agreement with these observations was a fourfold-increased H(+)-ATPase activity in the posterior intestine of animals acclimated to 60 ppt salinity. Interestingly, Na(+)-K(+)-ATPase activity was elevated in the anterior intestine and gill, but not in the posterior intestine. Apical acid secretion by isolated intestinal tissue mounted in Ussing chambers fitted with pH-stat titration systems increased after acclimation to hypersalinity in the anterior and posterior intestine, titrating >20% of secreted bicarbonate. In addition, net base secretion increased in hypersalinity-acclimated fish and was ∼70% dependent on serosal HCO(3)(-). Protein localization by immunohistochemistry confirmed the presence of the vacuolar-type H(+)-ATPase in the apical region of intestinal enterocytes. These results show that the H(+) pump, especially in the posterior intestine, plays an important role in hypersaline osmoregulation and that it likely has significant effects on HCO(3)(-) accumulation in the intestinal lumen and, therefore, the continued absorption of Cl(-) and water.
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Affiliation(s)
- S Guffey
- Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, Miami, Florida 33149, USA.
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Tresguerres M, Levin LR, Buck J. Intracellular cAMP signaling by soluble adenylyl cyclase. Kidney Int 2011; 79:1277-88. [PMID: 21490586 DOI: 10.1038/ki.2011.95] [Citation(s) in RCA: 156] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Soluble adenylyl cyclase (sAC) is a recently identified source of the ubiquitous second messenger cyclic adenosine 3',5' monophosphate (cAMP). sAC is distinct from the more widely studied source of cAMP, the transmembrane adenylyl cyclases (tmACs); its activity is uniquely regulated by bicarbonate anions, and it is distributed throughout the cytoplasm and in cellular organelles. Due to its unique localization and regulation, sAC has various functions in a variety of physiological systems that are distinct from tmACs. In this review, we detail the known functions of sAC, and we reassess commonly held views of cAMP signaling inside cells.
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Affiliation(s)
- Martin Tresguerres
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA
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Tresguerres M, Buck J, Levin LR. Physiological carbon dioxide, bicarbonate, and pH sensing. Pflugers Arch 2010; 460:953-64. [PMID: 20683624 DOI: 10.1007/s00424-010-0865-6] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Revised: 07/16/2010] [Accepted: 07/18/2010] [Indexed: 12/20/2022]
Abstract
In biological systems, carbon dioxide exists in equilibrium with bicarbonate and protons. The individual components of this equilibrium (i.e., CO₂, HCO₃⁻, and H(+)), which must be sensed to be able to maintain cellular and organismal pH, also function as signals to modulate multiple physiological functions. Yet, the molecular sensors for CO₂/HCO₃⁻/pH remained unknown until recently. Here, we review recent progress in delineating molecular and cellular mechanisms for sensing CO₂, HCO₃⁻, and pH.
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Affiliation(s)
- Martin Tresguerres
- Department of Pharmacology, Weill Cornell Medical College, Cornell University, New York, USA
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