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Higgins JA, Ramos DS, Gili S, Spetea C, Kanoski S, Ha D, McDonough AA, Youn JH. Stable potassium isotopes (41K/39K) track transcellular and paracellular potassium transport in biological systems. Front Physiol 2022; 13:1016242. [PMID: 36388124 PMCID: PMC9644202 DOI: 10.3389/fphys.2022.1016242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Accepted: 09/21/2022] [Indexed: 12/04/2022] Open
Abstract
As the most abundant cation in archaeal, bacterial, and eukaryotic cells, potassium (K+) is an essential element for life. While much is known about the machinery of transcellular and paracellular K transport–channels, pumps, co-transporters, and tight-junction proteins—many quantitative aspects of K homeostasis in biological systems remain poorly constrained. Here we present measurements of the stable isotope ratios of potassium (41K/39K) in three biological systems (algae, fish, and mammals). When considered in the context of our current understanding of plausible mechanisms of K isotope fractionation and K+ transport in these biological systems, our results provide evidence that the fractionation of K isotopes depends on transport pathway and transmembrane transport machinery. Specifically, we find that passive transport of K+ down its electrochemical potential through channels and pores in tight-junctions at favors 39K, a result which we attribute to a kinetic isotope effect associated with dehydration and/or size selectivity at the channel/pore entrance. In contrast, we find that transport of K+ against its electrochemical gradient via pumps and co-transporters is associated with less/no isotopic fractionation, a result that we attribute to small equilibrium isotope effects that are expressed in pumps/co-transporters due to their slower turnover rate and the relatively long residence time of K+ in the ion pocket. These results indicate that stable K isotopes may be able to provide quantitative constraints on transporter-specific K+ fluxes (e.g., the fraction of K efflux from a tissue by channels vs. co-transporters) and how these fluxes change in different physiological states. In addition, precise determination of K isotope effects associated with K+ transport via channels, pumps, and co-transporters may provide unique constraints on the mechanisms of K transport that could be tested with steered molecular dynamic simulations.
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Affiliation(s)
- John A. Higgins
- Department of Geosciences, Princeton University, Princeton, NJ, United States
- *Correspondence: John A. Higgins,
| | - Danielle Santiago Ramos
- Department of Marine and Coastal Science, Rutgers University, New Brunswick, NJ, United States
| | - Stefania Gili
- Department of Geosciences, Princeton University, Princeton, NJ, United States
| | - Cornelia Spetea
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
- Department of Molecular Biology, Princeton University, Princeton, NJ, United States
| | - Scott Kanoski
- Department of Human and Evolutionary Biology, University of Southern California, Los Angeles, CA, United States
| | - Darren Ha
- Department of Physiology and Neuroscience, University of Southern California Keck School of Medicine, Los Angeles, CA, United States
| | - Alicia A. McDonough
- Department of Physiology and Neuroscience, University of Southern California Keck School of Medicine, Los Angeles, CA, United States
| | - Jang H. Youn
- Department of Physiology and Neuroscience, University of Southern California Keck School of Medicine, Los Angeles, CA, United States
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2
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Seale AP, Breves JP. Endocrine and osmoregulatory responses to tidally-changing salinities in fishes. Gen Comp Endocrinol 2022; 326:114071. [PMID: 35697315 DOI: 10.1016/j.ygcen.2022.114071] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Revised: 06/06/2022] [Accepted: 06/07/2022] [Indexed: 12/15/2022]
Abstract
Salinity is one of the main physical properties that govern the distribution of fishes across aquatic habitats. In order to maintain their body fluids near osmotic set points in the face of salinity changes, euryhaline fishes rely upon tissue-level osmotically-induced responses and systemic endocrine signaling to direct adaptive ion-transport processes in the gill and other critical osmoregulatory organs. Some euryhaline teleosts inhabit tidally influenced waters such as estuaries where salinity can vary between fresh water (FW) and seawater (SW). The physiological adaptations that underlie euryhalinity in teleosts have been traditionally identified in fish held under steady-state conditions or following unidirectional transfers between FW and SW. Far fewer studies have employed salinity regimes that simulate the tidal cycles that some euryhaline fishes may experience in their native habitats. With an emphasis on prolactin (Prl) signaling and branchial ionocytes, this mini-review contrasts the physiological responses between euryhaline fish responding to tidal versus unidirectional changes in salinity. Three patterns that emerged from studying Mozambique tilapia (Oreochromis mossambicus) subjected to tidally-changing salinities include, 1) fish can compensate for continuous and marked changes in external salinity to maintain osmoregulatory parameters within narrow ranges, 2) tilapia maintain branchial ionocyte populations in a fashion similar to SW-acclimated fish, and 3) there is a shift from systemic to local modulation of Prl signaling.
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Affiliation(s)
- Andre P Seale
- Department of Human Nutrition, Food and Animal Sciences, University of Hawai'i at Mānoa, 1955 East-West Road, Honolulu, HI 96822, USA.
| | - Jason P Breves
- Department of Biology, Skidmore College, 815 N. Broadway, Saratoga Springs, NY 12866, USA
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3
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Gill transcriptome of the yellow peacock bass (Cichla ocellaris monoculus) exposed to contrasting physicochemical conditions. CONSERV GENET RESOUR 2022. [DOI: 10.1007/s12686-022-01284-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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4
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Inokuchi M, Hiroi J, Kaneko T. Why can Mozambique Tilapia Acclimate to Both Freshwater and Seawater? Insights From the Plasticity of Ionocyte Functions in the Euryhaline Teleost. Front Physiol 2022; 13:914277. [PMID: 35711299 PMCID: PMC9194847 DOI: 10.3389/fphys.2022.914277] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 05/17/2022] [Indexed: 11/27/2022] Open
Abstract
In teleost fishes, ionocytes in the gills are important osmoregulatory sites in maintaining ionic balance. During the embryonic stages before the formation of the gills, ionocytes are located in the yolk-sac membrane and body skin. In Mozambique tilapia embryos, quintuple-color immunofluorescence staining allowed us to classify ionocytes into four types: type I, showing only basolateral Na+/K+-ATPase (NKA) staining; type II, basolateral NKA and apical Na+, Cl− cotransporter 2; type III, basolateral NKA, basolateral Na+, K+, 2Cl− cotransporter 1a (NKCC1a) and apical Na+/H+ exchanger 3; and type IV, basolateral NKA, basolateral NKCC1a and apical cystic fibrosis transmembrane conductance regulator Cl− channel. The ionocyte population consisted mostly of type I, type II and type III in freshwater, while type I and IV dominated in seawater. In adult tilapia, dual observations of whole-mount immunocytochemistry and scanning electron microscopy showed morphofunctional alterations in ionocytes. After transfer from freshwater to seawater, while type-II ionocytes closed their apical openings to suspend ion absorption, type-III ionocytes with a concave surface were transformed into type IV with a pit via a transitory surface. The proposed model of functional classification of ionocytes can account not only for ion uptake in freshwater and ion secretion in seawater, but also for plasticity in ion-transporting functions of ionocytes in tilapia.
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Affiliation(s)
- Mayu Inokuchi
- Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, the University of Tokyo, Bunkyo, Japan
| | - Junya Hiroi
- Department of Anatomy, St. Marianna University School of Medicine, Kawasaki, Japan
| | - Toyoji Kaneko
- Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, the University of Tokyo, Bunkyo, Japan
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5
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Velotta JP, McCormick SD, Whitehead A, Durso CS, Schultz ET. Repeated Genetic Targets of Natural Selection Underlying Adaptation of Fishes to Changing Salinity. Integr Comp Biol 2022; 62:357-375. [PMID: 35661215 DOI: 10.1093/icb/icac072] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 05/16/2022] [Accepted: 05/05/2022] [Indexed: 11/12/2022] Open
Abstract
Ecological transitions across salinity boundaries have led to some of the most important diversification events in the animal kingdom, especially among fishes. Adaptations accompanying such transitions include changes in morphology, diet, whole-organism performance, and osmoregulatory function, which may be particularly prominent since divergent salinity regimes make opposing demands on systems that maintain ion and water balance. Research in the last decade has focused on the genetic targets underlying such adaptations, most notably by comparing populations of species that are distributed across salinity boundaries. Here, we synthesize research on the targets of natural selection using whole-genome approaches, with a particular emphasis on the osmoregulatory system. Given the complex, integrated and polygenic nature of this system, we expected that signatures of natural selection would span numerous genes across functional levels of osmoregulation, especially salinity sensing, hormonal control, and cellular ion exchange mechanisms. We find support for this prediction: genes coding for V-type, Ca2+, and Na+/K+-ATPases, which are key cellular ion exchange enzymes, are especially common targets of selection in species from six orders of fishes. This indicates that while polygenic selection contributes to adaptation across salinity boundaries, changes in ATPase enzymes may be of particular importance in supporting such transitions.
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Affiliation(s)
- Jonathan P Velotta
- Department of Biological Sciences, University of Denver, Denver, CO 80210, USA
| | - Stephen D McCormick
- USGS, Eastern Ecological Science Center, Conte Anadromous Fish Research Center, Turners Falls, MA 01376, USA.,Department of Biology, University of Massachusetts, Amherst, MA, 01003USA
| | - Andrew Whitehead
- Department of Environmental Toxicology, University of California, Davis, Davis, CA 95616, USA
| | - Catherine S Durso
- Department of Computer Science, University of Denver, Denver, CO 80210, USA
| | - Eric T Schultz
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT 06269, USA
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6
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Breves JP, Nelson NN, Koltenyuk V, Petro-Sakuma CK, Celino-Brady FT, Seale AP. Enhanced expression of ncc1 and clc2c in the kidney and urinary bladder accompanies freshwater acclimation in Mozambique tilapia. Comp Biochem Physiol A Mol Integr Physiol 2021; 260:111021. [PMID: 34174427 PMCID: PMC8355173 DOI: 10.1016/j.cbpa.2021.111021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Revised: 06/19/2021] [Accepted: 06/21/2021] [Indexed: 11/15/2022]
Abstract
Euryhaline fishes maintain hydromineral balance in a broad range of environmental salinities via the activities of multiple osmoregulatory organs, namely the gill, gastrointestinal tract, skin, kidney, and urinary bladder. Teleosts residing in freshwater (FW) environments are faced with the diffusive loss of ions and the osmotic gain of water, and, therefore, the kidney and urinary bladder reabsorb Na+ and Cl- to support the production of dilute urine. Nonetheless, the regulated pathways for Na+ and Cl- transport by euryhaline fishes, especially in the urinary bladder, have not been fully resolved. Here, we first investigated the ultrastructure of epithelial cells within the urinary bladder of FW-acclimated Mozambique tilapia (Oreochromis mossambicus) by electron microscopy. We then investigated whether tilapia employ Na+/Cl- cotransporter 1 (Ncc1) and Clc family Cl- channel 2c (Clc2c) for the reabsorption of Na+ and Cl- by the kidney and urinary bladder. We hypothesized that levels of their associated gene transcripts vary inversely with environmental salinity. In whole kidney and urinary bladder homogenates, ncc1 and clc2c mRNA levels were markedly higher in steady-state FW- versus SW (seawater)-acclimated tilapia. Following transfer from SW to FW, ncc1 and clc2c in both the kidney and urinary bladder were elevated within 48 h. A concomitant increase in branchial ncc2, and decreases in Na+/K+/2Cl-cotransporter 1a (nkcc1a) and cystic fibrosis transmembrane regulator 1 (cftr1) levels indicated a transition from Na+ and Cl- secretion to absorption by the gills in parallel with the identified renal and urinary bladder responses to FW transfer. Our findings suggest that Ncc1 and Clc2c contribute to the functional plasticity of the kidney and urinary bladder in tilapia.
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Affiliation(s)
- Jason P Breves
- Department of Biology, Skidmore College, Saratoga Springs, NY 12866, USA.
| | - Nastasia N Nelson
- Department of Biology, Skidmore College, Saratoga Springs, NY 12866, USA
| | - Victor Koltenyuk
- Department of Biology, Skidmore College, Saratoga Springs, NY 12866, USA
| | - Cody K Petro-Sakuma
- Department of Human Nutrition, Food and Animal Sciences, University of Hawai'i at Mānoa, 1955 East-West Road, Honolulu, HI 96822, USA
| | - Fritzie T Celino-Brady
- Department of Human Nutrition, Food and Animal Sciences, University of Hawai'i at Mānoa, 1955 East-West Road, Honolulu, HI 96822, USA
| | - Andre P Seale
- Department of Human Nutrition, Food and Animal Sciences, University of Hawai'i at Mānoa, 1955 East-West Road, Honolulu, HI 96822, USA
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7
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Effects of Dissolved Potassium on Growth Performance, Body Composition, and Welfare of Juvenile African Catfish (Clarias gariepinus). FISHES 2021. [DOI: 10.3390/fishes6020011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Optimal crop production in aquaponics is influenced by water pH and potassium concentrations. The addition of potassium hydroxide (KOH) into the recirculating aquaculture system (RAS) may benefit aquaponics by increasing the water pH for better biofilter activity and supplementing K for better plant growth and quality. We investigated the growth, feed conversion, body composition and welfare indicators of juvenile African catfish (Clarias gariepinus) treated with four concentrations of K (K0 = 2, K200 = 218, K400 = 418, and K600 = 671 mg L−1). While growth, feed conversion and final body composition were unaffected, the feeding time and individual resting significantly increased with increasing K+. The swimming activity and agonistic behavior were reduced significantly under increased concentrations of K+. Leftover feed and the highest number of skin lesions were observed under K600. We suggest that K+ concentrations between 200 and 400 mg L−1 can improve the welfare status of juvenile African catfish. This enables the application of KOH in RAS to supply alkalinity to achieve optimum nitrification at minimum water exchange and improve the nutritional profile of the process water with benefits for the welfare status of African catfish and aquaponics plant production and quality.
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8
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Lee CY, Horng JL, Liu ST, Lin LY. Exposure to copper nanoparticles impairs ion uptake, and acid and ammonia excretion by ionocytes in zebrafish embryos. CHEMOSPHERE 2020; 261:128051. [PMID: 33113650 DOI: 10.1016/j.chemosphere.2020.128051] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 08/15/2020] [Accepted: 08/17/2020] [Indexed: 06/11/2023]
Abstract
The potential toxicity of copper nanoparticles (CuNPs) to early stages of fishes is not fully understood, and little is known about their effects on ionocytes and associated functions. This study used zebrafish embryos as a model to investigate the toxic effects of CuNPs on two subtypes of ionocytes. Zebrafish embryos were exposed to 0.1, 1, and 3 mg L-1 CuNPs for 96 h. After exposure, whole-body Na+ and Ca2+ contents were significantly reduced at ≥0.1 mg L-1, while the K+ content had decreased at ≥1 mg L-1. H+ and NH4+ excretion by the skin significantly decreased at ≥1 mg L-1. The number of living ionocytes labeled with rhodamine-123 had significantly decreased with ≥0.1 mg L-1 CuNPs. The ionocyte subtypes of H+-ATPase-rich (HR) and Na+/K+-ATPase-rich (NaR) cells were labeled by immunostaining and had decreased with ≥1 mg L-1. Shrinkage of the apical opening of ionocytes was revealed by scanning electronic microscopy. Functional impairment was also reflected by changes in gene expressions, including ion transporters/channels and Ca2+-regulatory hormones. This study shows that CuNP exposure can impair two subtypes of ionocytes and their associated functions, including Na+/Ca2+ uptake and H+/NH4+ excretion in zebrafish embryos.
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Affiliation(s)
- Chih-Ying Lee
- Department of Life Science, School of Life Science, National Taiwan Normal University, Taipei, Taiwan; Division of Pediatric Hematology and Oncology, Department of Pediatrics, Taipei Veterans General Hospital, Taipei, Taiwan; Department of Pediatrics, Faculty of Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan
| | - Jiun-Lin Horng
- Department of Anatomy and Cell Biology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Sian-Tai Liu
- Department of Life Science, School of Life Science, National Taiwan Normal University, Taipei, Taiwan
| | - Li-Yih Lin
- Department of Life Science, School of Life Science, National Taiwan Normal University, Taipei, Taiwan.
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9
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Potassium Regulation in Medaka (Oryzias latipes) Larvae Acclimated to Fresh Water: Passive Uptake and Active Secretion by the Skin Cells. Sci Rep 2017; 7:16215. [PMID: 29176723 PMCID: PMC5701230 DOI: 10.1038/s41598-017-16381-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 11/13/2017] [Indexed: 01/29/2023] Open
Abstract
Molecular mechanisms of Na+, Cl−, and Ca2+ regulation in ionocytes of fish have been well investigated. However, the regulatory mechanism of K+ in fishes has been largely unknown. In this study, we investigated the mechanism of K+ regulation in medaka larvae acclimated to fresh water. Using a scanning ion-selective electrode technique (SIET) to measure the K+ fluxes at skin cells, significant K+ effluxes were found at ionocytes; in contrast, significant K+ influxes were found at the boundaries between keratinocytes. High K+ water (HK) acclimation induced the K+ effluxes at ionocytes and suppressed the K+ influxes at keratinocytes. The K+ effluxes of ionocytes were suppressed by VU591, bumetanide and ouabain. The K+ influxes of keratinocytes were suppressed by TAP. In situ hybridization analysis showed that mRNA of ROMKa was expressed by ionocytes in the skin and gills of medaka larvae. Quantitative PCR showed that mRNA levels of ROMKa and NKCC1a in gills of adult medaka were upregulated after HK acclimation. This study suggests that medaka obtain K+ through a paracellular pathway between keratinocytes and extrude K+ through ionocytes; apical ROMKa and basolateral NKCC1a are involved in the K+ secretion by ionocytes.
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10
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Lee JD, Lee MH, Yang WK, Wang KL, Lee TH. Differential Expression of Renal Outer Medullary K + Channel and Voltage-gated K + Channel 7.1 in Bladder Urothelium of Patients With Interstitial Cystitis/Painful Bladder Syndrome. Urology 2017; 101:169.e1-169.e5. [DOI: 10.1016/j.urology.2016.11.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2016] [Revised: 10/04/2016] [Accepted: 11/04/2016] [Indexed: 12/27/2022]
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11
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Watanabe S, Itoh K, Kaneko T. Prolactin and cortisol mediate the maintenance of hyperosmoregulatory ionocytes in gills of Mozambique tilapia: Exploring with an improved gill incubation system. Gen Comp Endocrinol 2016; 232:151-9. [PMID: 27118703 DOI: 10.1016/j.ygcen.2016.04.024] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Revised: 03/23/2016] [Accepted: 04/22/2016] [Indexed: 10/21/2022]
Abstract
Endocrine control of osmoregulation is essential for teleosts to adapt to various aquatic environments. Prolactin (PRL) is known as a fundamental endocrine factor for hyperosmoregulation in teleost fishes, acting on ionocytes in the gills to maintain ion concentrations of body fluid within narrow physiological ranges in freshwater conditions. Cortisol is also known as an osmoregulation-related steroid in teleosts; however, its precise function is still controversial. Here, we investigated more detailed effects of PRL and roles of cortisol on ionocytes of Mozambique tilapia (Oreochromis mossambicus) in freshwater, using an improved gill filament incubation system. This incubation system resulted in enhanced cell viability, as evaluated using the dead cell marker propidium iodide. PRL was shown to maintain the density of freshwater-type ionocytes in isolated gill filaments; this effect of PRL is not achieved by the activation of cell proliferation, but by the maintenance of existing ionocytes. Cortisol alone did not show any distinct effect on ionocyte density in isolated gill filaments. We also assessed effects of PRL and cortisol on relative mRNA levels of NCC2, NHE3, NKAa1a, and NKAa1b. PRL maintained relative NCC2 and NKAa1a mRNA abundance, and cortisol showed a stimulatory effect on relative NCC2 and NKAa1a mRNA levels in combination with PRL, though cortisol alone exerted no effect on these genes. An increase in NKAa1b mRNA abundance was detected in cortisol-treated groups. PRL treatment also maintained normal NCC2 localization at the apical membrane of the ionocytes. These results indicate that PRL maintains freshwater-type ionocytes, and that cortisol stimulates the function of ionocytes maintained by PRL.
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Affiliation(s)
- Soichi Watanabe
- Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan.
| | - Kohei Itoh
- Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan
| | - Toyoji Kaneko
- Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan
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12
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Inokuchi M, Breves JP, Moriyama S, Watanabe S, Kaneko T, Lerner DT, Grau EG, Seale AP. Prolactin 177, prolactin 188, and extracellular osmolality independently regulate the gene expression of ion transport effectors in gill of Mozambique tilapia. Am J Physiol Regul Integr Comp Physiol 2015; 309:R1251-63. [PMID: 26377558 DOI: 10.1152/ajpregu.00168.2015] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 09/11/2015] [Indexed: 02/03/2023]
Abstract
This study characterized the local effects of extracellular osmolality and prolactin (PRL) on branchial ionoregulatory function of a euryhaline teleost, Mozambique tilapia (Oreochromis mossambicus). First, gill filaments were dissected from freshwater (FW)-acclimated tilapia and incubated in four different osmolalities, 280, 330, 380, and 450 mosmol/kg H2O. The mRNA expression of Na(+)/K(+)-ATPase α1a (NKA α1a) and Na(+)/Cl(-) cotransporter (NCC) showed higher expression with decreasing media osmolalities, while Na(+)/K(+)/2Cl(-) cotransporter 1a (NKCC1a) and PRL receptor 2 (PRLR2) mRNA levels were upregulated by increases in media osmolality. We then incubated gill filaments in media containing ovine PRL (oPRL) and native tilapia PRLs (tPRL177 and tPRL188). oPRL and the two native tPRLs showed concentration-dependent effects on NCC, NKAα1a, and PRLR1 expression; Na(+)/H(+) exchanger 3 (NHE3) expression was increased by 24 h of incubation with tPRLs. Immunohistochemical observation showed that oPRL and both tPRLs maintained a high density of NCC- and NKA-immunoreactive ionocytes in cultured filaments. Furthermore, we found that tPRL177 and tPRL188 differentially induce expression of these ion transporters, according to incubation time. Together, these results provide evidence that ionocytes of Mozambique tilapia may function as osmoreceptors, as well as directly respond to PRL to modulate branchial ionoregulatory functions.
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Affiliation(s)
- Mayu Inokuchi
- Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, Hawaii; Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo, Japan; and
| | - Jason P Breves
- Department of Biology, Skidmore College, Saratoga Springs, New York
| | - Shunsuke Moriyama
- School of Marine Biosciences, Kitasato University, Sagamihara, Kanagawa, Japan
| | - Soichi Watanabe
- Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo, Japan; and
| | - Toyoji Kaneko
- Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo, Japan; and
| | - Darren T Lerner
- Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, Hawaii; University of Hawaii Sea Grant College Program, University of Hawaii at Manoa, Honolulu, Hawaii
| | - E Gordon Grau
- Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, Hawaii; University of Hawaii Sea Grant College Program, University of Hawaii at Manoa, Honolulu, Hawaii
| | - Andre P Seale
- Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, Hawaii
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13
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Furukawa F, Watanabe S, Seale AP, Breves JP, Lerner DT, Grau EG, Kaneko T. In vivo and in vitro effects of high-K(+) stress on branchial expression of ROMKa in seawater-acclimated Mozambique tilapia. Comp Biochem Physiol A Mol Integr Physiol 2015; 187:111-8. [PMID: 26021981 DOI: 10.1016/j.cbpa.2015.05.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Revised: 05/17/2015] [Accepted: 05/20/2015] [Indexed: 11/26/2022]
Abstract
Recently, a teleost ortholog of renal outer medullary K(+) channel (ROMK) expressed in gill ionocytes (ROMKa) has emerged as a primary K(+)-excreting pathway in fish. However, the mechanisms by which ROMKa expression is regulated in response to perturbations of plasma K(+) levels are unknown. In this study, we aimed to identify potential links between the endocrine system and K(+) regulation in a euryhaline fish. We assessed time-course changes in multiple endocrine parameters, including plasma cortisol and gene expression of branchial glucocorticoid and mineralocorticoid receptors (GR1, GR2, and MR) and pituitary hormones, in seawater (SW)-acclimated Mozambique tilapia (Oreochromis mossambicus) exposed to high-K(+) (H-K) SW. Exposure to H-K SW elicited little effects on plasma cortisol or mRNA levels of GRs and pituitary hormones. Since plasma K(+) and branchial ROMKa expression was increased within 6h after H-K treatment in vivo, the effect of high K(+) was subsequently tested in a gill filament incubation experiment using media with differing K(+) concentrations. ROMKa mRNA levels were induced following incubation of filaments in H-K medium for 6h. The present study is the first to demonstrate that the expression of ROMKa in teleost ionocytes can respond to high K(+) conditions independent from systemic signaling.
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Affiliation(s)
- Fumiya Furukawa
- Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan.
| | - Soichi Watanabe
- Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan
| | - Andre P Seale
- Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, HI 96744, USA
| | - Jason P Breves
- Department of Biology, Skidmore College, Saratoga Springs, NY 12866, USA
| | - Darren T Lerner
- Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, HI 96744, USA
| | - E Gordon Grau
- Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, HI 96744, USA
| | - Toyoji Kaneko
- Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan
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14
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Guh YJ, Lin CH, Hwang PP. Osmoregulation in zebrafish: ion transport mechanisms and functional regulation. EXCLI JOURNAL 2015; 14:627-59. [PMID: 26600749 PMCID: PMC4650948 DOI: 10.17179/excli2015-246] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 04/21/2015] [Indexed: 12/21/2022]
Abstract
Fish, like mammals, have to maintain their body fluid ionic and osmotic homeostasis through sophisticated iono-/osmoregulation mechanisms, which are conducted mainly by ionocytes of the gill (the skin in embryonic stages), instead of the renal tubular cells in mammals. Given the advantages in terms of genetic database availability and manipulation, zebrafish is an emerging model for research into regulatory and integrative physiology. At least five types of ionocytes, HR, NaR, NCC, SLC26, and KS cells, have been identified to carry out Na(+) uptake/H(+) secretion/NH4 (+) excretion, Ca(2+) uptake, Na(+)/Cl(-) uptake, K(+) secretion, and Cl(-) uptake/HCO3 (-) secretion, respectively, through distinct sets of transporters. Several hormones, namely isotocin, prolactin, cortisol, stanniocalcin-1, calcitonin, endothelin-1, vitamin D, parathyorid hormone 1, catecholamines, and the renin-angiotensin-system, have been demonstrated to positively or negatively regulate ion transport through specific receptors at different ionocytes stages, at either the transcriptional/translational or posttranslational level. The knowledge obtained using zebrafish answered many long-term contentious or unknown issues in the field of fish iono-/osmoregulation. The homology of ion transport pathways and hormone systems also means that the zebrafish model informs studies on mammals or other animal species, thereby providing insights into related fields.
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Affiliation(s)
- Ying-Jey Guh
- Institute of Cellular and Organismic Biology, Academia Sinica, Nakang, Taipei, Taiwan ; Institute of Biological Chemistry, Academia Sinica, Nakang, Taipei, Taiwan
| | - Chia-Hao Lin
- National Institute for Basic Biology, Myodaiji-cho, Okazaki, 444-8787, Japan
| | - Pung-Pung Hwang
- Institute of Cellular and Organismic Biology, Academia Sinica, Nakang, Taipei, Taiwan
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