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Malintha GHT, Woo DW, Celino-Brady FT, Seale AP. Temperature modulates the osmosensitivity of tilapia prolactin cells. Sci Rep 2023; 13:20217. [PMID: 37980366 PMCID: PMC10657356 DOI: 10.1038/s41598-023-47044-5] [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: 01/28/2023] [Accepted: 11/08/2023] [Indexed: 11/20/2023] Open
Abstract
In euryhaline fish, prolactin (Prl) plays an essential role in freshwater (FW) acclimation. In the euryhaline and eurythermal Mozambique tilapia, Oreochromis mossambicus, Prl cells are model osmoreceptors, recently described to be thermosensitive. To investigate the effects of temperature on osmoreception, we incubated Prl cells of tilapia acclimated to either FW or seawater (SW) in different combinations of temperatures (20, 26 and 32 °C) and osmolalities (280, 330 and 420 mOsm/kg) for 6 h. Release of both Prl isoforms, Prl188 and Prl177, increased in hyposmotic media and were further augmented with a rise in temperature. Hyposmotically-induced release of Prl188, but not Prl177, was suppressed at 20 °C. In SW fish, mRNA expression of prl188 increased with rising temperatures at lower osmolalities, while and prl177 decreased at 32 °C and higher osmolalities. In Prl cells of SW-acclimated tilapia incubated in hyperosmotic media, the expressions of Prl receptors, prlr1 and prlr2, and the stretch-activated Ca2+ channel, trpv4,decreased at 32 °C, suggesting the presence of a cellular mechanism to compensate for elevated Prl release. Transcription factors, pou1f1, pou2f1b, creb3l1, cebpb, stat3, stat1a and nfat1c, known to regulate prl188 and prl177, were also downregulated at 32 °C. Our findings provide evidence that osmoreception is modulated by temperature, and that both thermal and osmotic responses vary with acclimation salinity.
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Affiliation(s)
- G H T Malintha
- Department of Human Nutrition, Food and Animal Sciences, University of Hawai'i at Mānoa, 1955 East-West Road, Honolulu, HI, 96822, USA
| | - Daniel W Woo
- 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
- Division of Genetics, Oregon National Primate Research Center, Oregon Health and Science University, Beaverton, OR, 97006, 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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Malintha GHT, Celino-Brady FT, Stoytcheva ZR, Seale AP. Osmosensitive transcription factors in the prolactin cell of a euryhaline teleost. Comp Biochem Physiol A Mol Integr Physiol 2023; 278:111356. [PMID: 36535574 PMCID: PMC9911408 DOI: 10.1016/j.cbpa.2022.111356] [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: 10/12/2022] [Revised: 12/14/2022] [Accepted: 12/14/2022] [Indexed: 12/23/2022]
Abstract
In euryhaline fish, prolactin (Prl) plays a key role in freshwater acclimation. Prl release in the rostral pars distalis (RPD) of the pituitary is directly stimulated by a fall in extracellular osmolality. Recently, we identified several putative transcription factor modules (TFM) predicted to bind to the promoter regions of the two prl isoforms in Mozambique tilapia, Oreochromis mossambicus. We characterized the effects of extracellular osmolality on the activation of these TFMs from RPDs, in vivo and in vitro. OCT1_PIT1 01, CEBP_CEBP 01 and BRNF_RXRF 01 were significantly activated in freshwater (FW)- acclimated tilapia RPDs while SORY_PAX3 02 and SP1F_SP1F 06, SP1F_SP1F 09 were significantly activated in seawater (SW)- counterparts. Short-term incubation of SW- acclimated tilapia RPDs in hyposmotic media (280 mOsm/kg) resulted in activation of CAAT_AP1F 01, OCT1_CEBP 01, AP1F_SMAD 01, GATA_SP1F 01, SORY_PAX6 01 and CREB_EBOX 02, EBOX_AP2F 01, EBOX_MITF 01 while hyperosmotic media (420 mOsm/kg) activated SORY_PAX3 02 and AP1F_SMAD 01 in FW- tilapia. Short-term incubation of dispersed Prl cells from FW- acclimated fish exposed to hyperosmotic conditions decreased pou1f1, pou2f1b, stat3, stat1a and ap1b1 expression, while pou1f1, pou2f1b, and stat3 were inversely related to osmolality in their SW- counterparts. Further, in Prl cells of SW- tilapia, creb3l1 was suppressed in hyposmotic media. Collectively, our results indicate that multiple TFMs are involved in regulating prl transcription at different acclimation salinities and, together, they modulate responses of Prl cells to changes in extracellular osmolality. These responses reflect the complexity of osmosensitive molecular regulation of the osmoreceptive Prl cell of a euryhaline teleost.
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Affiliation(s)
- G H T Malintha
- Department of Human Nutrition, Food and Animal Sciences, University of Hawai'i at Mānoa, Honolulu, HI 96822, USA
| | - Fritzie T Celino-Brady
- Department of Human Nutrition, Food and Animal Sciences, University of Hawai'i at Mānoa, Honolulu, HI 96822, USA
| | - Zoia R Stoytcheva
- Department of Human Nutrition, Food and Animal Sciences, University of Hawai'i at Mānoa, Honolulu, HI 96822, USA
| | - Andre P Seale
- Department of Human Nutrition, Food and Animal Sciences, University of Hawai'i at Mānoa, Honolulu, HI 96822, USA.
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Hewage TMG, Woo DW, Celino-Brady FT, Seale AP. Temperature modulates the osmosensitivity of tilapia prolactin cells. RESEARCH SQUARE 2023:rs.3.rs-2524830. [PMID: 36909603 PMCID: PMC10002831 DOI: 10.21203/rs.3.rs-2524830/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/06/2023]
Abstract
In euryhaline fish, prolactin (Prl) plays an essential role in freshwater (FW) acclimation. In the euryhaline and eurythermal Mozambique tilapia, Oreochromis mossambicus, Prl cells are model osmoreceptors, recently described to be thermosensitive. To investigate the effects of temperature on osmoreception, we incubated Prl cells of tilapia acclimated to either FW or seawater (SW) in different temperature (20, 26 and 32°C) and osmolality (280, 330 and 420 mOsm/kg) combinations for 6 h. Release of both Prl isoforms, Prl188 and Prl177, increased in hyposmotic media and were further augmented with a rise in temperature. Hyposmotically-induced release of Prl188 was inhibited at 20°C. In SW fish, mRNA expression of prl188 and prl177 showed direct and inverse relationships with temperature, respectively. In SW-acclimated tilapia Prl cells incubated in hyperosmotic media, Prl receptors, prlr1 and prlr2, and the stretch-activated Ca2+ channel, trpv4, were inhibited at 32°C, suggesting the presence of a cellular mechanism to compensate for elevated Prl release. Transcription factors, pou1f1, pou2f1b, creb3l1, cebpb, stat3, stat1a and nfat1c, known to regulate prl188 and prl177, were also downregulated at 32°C. Our findings provide evidence that osmoreception is modulated by temperature, and that both thermal and osmotic responses vary with acclimation salinity.
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Rahmad Royan M, Siddique K, Nourizadeh-Lillabadi R, Weltzien FA, Henkel C, Fontaine R. Functional and developmental heterogeneity of pituitary lactotropes in medaka. Gen Comp Endocrinol 2023; 330:114144. [PMID: 36270338 DOI: 10.1016/j.ygcen.2022.114144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 10/06/2022] [Accepted: 10/10/2022] [Indexed: 11/06/2022]
Abstract
In fish, prolactin-producing cells (lactotropes) are located in the anterior part of the pituitary and play an essential role in osmoregulation. However, small satellite lactotrope clusters have been described in other parts of the pituitary in several species. The functional and developmental backgrounds of these satellite clusters are not known. We recently discovered two distinct prolactin-expressing cell types in Japanese medaka (Oryzias latipes), a euryhaline species, using single cell transcriptomics. In the present study, we characterize these two transcriptomically distinct lactotrope cell types and explore the hypothesis that they represent spatially distinct cell clusters, as found in other species. Single cell RNA sequencing shows that one of the two lactotrope cell types exhibits an expression profile similar to that of stem cell-like folliculo-stellate cell populations. Using in situ hybridization, we show that the medaka pituitary often develops additional small satellite lactotrope cell clusters, like in other teleost species. These satellite clusters arise early during development and grow in cell number throughout life regardless of the animal's sex. Surprisingly, our data do not show a correspondence between the stem cell-like lactotropes and these satellite lactotrope clusters. Instead, our data support a scenario in which the stem cell-like lactotropes are an intrinsic stage in the development of every spatially distinct lactotrope cluster. In addition, lactotrope activity in both spatially distinct lactotrope clusters decreases when environmental salinity increases, supporting their role in osmoregulation. However, this decrease appears weaker in the satellite lactotrope cell clusters, suggesting that these lactotropes are regulated differently.
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Affiliation(s)
- Muhammad Rahmad Royan
- Physiology Unit, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Ås, Norway
| | - Khadeeja Siddique
- Physiology Unit, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Ås, Norway
| | | | - Finn-Arne Weltzien
- Physiology Unit, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Ås, Norway
| | - Christiaan Henkel
- Physiology Unit, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Ås, Norway.
| | - Romain Fontaine
- Physiology Unit, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Ås, Norway.
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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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Woo DW, Malintha GHT, Celino-Brady FT, Yamaguchi Y, Breves JP, Seale AP. Tilapia prolactin cells are thermosensitive osmoreceptors. Am J Physiol Regul Integr Comp Physiol 2022; 322:R609-R619. [PMID: 35438003 DOI: 10.1152/ajpregu.00027.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Prolactin (PRL) cells within the rostral pars distalis (RPD) of euryhaline and eurythermal Mozambique tilapia, Oreochromis mossambicus, rapidly respond to a hyposmotic stimulus by releasing two distinct PRL isoforms, PRL188 and PRL177. Here, we describe how environmentally relevant temperature changes affected mRNA levels of PRL188 and PRL177 and the release of immunoreactive prolactins from RPDs and dispersed PRL cells. When applied under isosmotic conditions (330 mOsm/kg), a 6 °C rise in temperature stimulated the release of PRL188 and PRL177 from both RPDs and dispersed PRL cells under perifusion. When exposed to this same change in temperature, ~50% of dispersed PRL cells gradually increased in volume by ~8%, a response partially inhibited by the water channel blocker, mercuric chloride. Following their response to increased temperature, PRL cells remained responsive to a hyposmotic stimulus (280 mOsm/kg). The mRNA expression of transient potential vanilloid 4, a Ca2+-channel involved in hyposomotically-induced PRL release, was elevated in response to a rise in temperature in dispersed PRL cells and RPDs at 6 and 24 h, respectively; prl188 and prl177 mRNAs were unaffected. Our findings indicate that thermosensitive PRL release is mediated, at least partially, through a cell-volume dependent pathway similar to how osmoreceptive PRL release is achieved.
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Affiliation(s)
- Daniel W Woo
- Department of Human Nutrition, Food and Animal Sciences, University of Hawaii at Manoa, Honolulu, HI, United States
| | - G H T Malintha
- Department of Human Nutrition, Food and Animal Sciences, University of Hawaii at Manoa, Honolulu, HI, United States
| | - Fritzie T Celino-Brady
- Department of Human Nutrition, Food and Animal Sciences, University of Hawaii at Manoa, Honolulu, HI, United States
| | - Yoko Yamaguchi
- Institute of Agricultural and Life Sciences, Academic Assembly, Shimane University, Matsue, Japan
| | - Jason P Breves
- Department of Biology, Skidmore College, Saratoga Springs, NY, United States
| | - Andre P Seale
- Department of Human Nutrition, Food and Animal Sciences, University of Hawaii at Manoa, Honolulu, HI, United States
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Seale AP, Malintha GHT, Celino-Brady FT, Head T, Belcaid M, Yamaguchi Y, Lerner DT, Baltzegar DA, Borski RJ, Stoytcheva ZR, Breves JP. Transcriptional regulation of prolactin in a euryhaline teleost: Characterisation of gene promoters through in silico and transcriptome analyses. J Neuroendocrinol 2020; 32:e12905. [PMID: 32996203 PMCID: PMC8612711 DOI: 10.1111/jne.12905] [Citation(s) in RCA: 6] [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: 02/08/2020] [Revised: 07/31/2020] [Accepted: 08/26/2020] [Indexed: 12/20/2022]
Abstract
The sensitivity of prolactin (Prl) cells of the Mozambique tilapia (Oreochromis mossambicus) pituitary to variations in extracellular osmolality enables investigations into how osmoreception underlies patterns of hormone secretion. Through the actions of their main secretory products, Prl cells play a key role in supporting hydromineral balance of fishes by controlling the major osmoregulatory organs (ie, gill, intestine and kidney). The release of Prl from isolated cells of the rostral pars distalis (RPD) occurs in direct response to physiologically relevant reductions in extracellular osmolality. Although the particular signal transduction pathways that link osmotic conditions to Prl secretion have been identified, the processes that underlie hyposmotic induction of prl gene expression remain unknown. In this short review, we describe two distinct tilapia gene loci that encode Prl177 and Prl188 . From our in silico analyses of prl177 and prl188 promoter regions (approximately 1000 bp) and a transcriptome analysis of RPDs from fresh water (FW)- and seawater (SW)-acclimated tilapia, we propose a working model for how multiple transcription factors link osmoreceptive processes with adaptive patterns of prl177 and prl188 gene expression. We confirmed via RNA-sequencing and a quantitative polymerase chain reaction that multiple transcription factors emerging as predicted regulators of prl gene expression are expressed in the RPD of tilapia. In particular, gene transcripts encoding pou1f1, stat3, creb3l1, pbxip1a and stat1a were highly expressed; creb3l1, pbxip1a and stat1a were elevated in fish acclimated to SW vs FW. Combined, our in silico and transcriptome analyses set a path for resolving how adaptive patterns of Prl secretion are achieved via the integration of osmoreceptive processes with the control of prl gene transcription.
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Affiliation(s)
- Andre P. Seale
- Department of Human Nutrition, Food and Animal Sciences, University of Hawai’i at Mānoa, Honolulu, HI, USA
| | | | - Fritzie T. Celino-Brady
- Department of Human Nutrition, Food and Animal Sciences, University of Hawai’i at Mānoa, Honolulu, HI, USA
| | - Tony Head
- Department of Human Nutrition, Food and Animal Sciences, University of Hawai’i at Mānoa, Honolulu, HI, USA
| | - Mahdi Belcaid
- Hawai’i Institute of Marine Biology, University of Hawai’i at Mānoa, Kaneohe, HI, USA
| | - Yoko Yamaguchi
- Institute of Agricultural and Life Sciences, Academic Assembly, Shimane University, Matsue, Japan
| | - Darren T. Lerner
- University of Hawai’i Sea Grant College Program, University of Hawai’i at Mānoa, Honolulu, HI, USA
| | - David A. Baltzegar
- Genomic Sciences Laboratory, Office of Research and Innovation, North Carolina State University, Raleigh, NC, USA
| | - Russell J. Borski
- Department of Biological Sciences, North Carolina State University, Raleigh, NC, USA
| | - Zoia R. Stoytcheva
- Department of Human Nutrition, Food and Animal Sciences, University of Hawai’i at Mānoa, Honolulu, HI, USA
| | - Jason P. Breves
- Department of Biology, Skidmore College, Saratoga Springs, NY, USA
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Dobolyi A, Oláh S, Keller D, Kumari R, Fazekas EA, Csikós V, Renner É, Cservenák M. Secretion and Function of Pituitary Prolactin in Evolutionary Perspective. Front Neurosci 2020; 14:621. [PMID: 32612510 PMCID: PMC7308720 DOI: 10.3389/fnins.2020.00621] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2020] [Accepted: 05/19/2020] [Indexed: 12/16/2022] Open
Abstract
The hypothalamo-pituitary system developed in early vertebrates. Prolactin is an ancient vertebrate hormone released from the pituitary that exerts particularly diverse functions. The purpose of the review is to take a comparative approach in the description of prolactin, its secretion from pituitary lactotrophs, and hormonal functions. Since the reproductive and osmoregulatory roles of prolactin are best established in a variety of species, these functions are the primary subjects of discussion. Different types of prolactin and prolactin receptors developed during vertebrate evolution, which will be described in this review. The signal transduction of prolactin receptors is well conserved among vertebrates enabling us to describe the whole subphylum. Then, the review focuses on the regulation of prolactin release in mammals as we have the most knowledge on this class of vertebrates. Prolactin secretion in response to different reproductive stimuli, such as estrogen-induced release, mating, pregnancy and suckling is detailed. Reproduction in birds is different from that in mammals in several aspects. Prolactin is released during incubation in avian species whose regulation and functional significance are discussed. Little information is available on prolactin in reptiles and amphibians; therefore, they are mentioned only in specific cases to explain certain evolutionary aspects. In turn, the osmoregulatory function of prolactin is well established in fish. The different types of pituitary prolactin in fish play particularly important roles in the adaptation of eutherian species to fresh water environments. To achieve this function, prolactin is released from lactotrophs in hyposmolarity, as they are directly osmosensitive in fish. In turn, the released prolactin acts on branchial epithelia, especially ionocytes of the gill to retain salt and excrete water. This review will highlight the points where comparative data give new ideas or suggest new approaches for investigation in other taxa.
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Affiliation(s)
- Arpád Dobolyi
- MTA-ELTE Laboratory of Molecular and Systems Neurobiology, Department of Physiology and Neurobiology, Institute of Biology, Eötvös Loránd University, Budapest, Hungary
- Laboratory of Neuromorphology, Department of Anatomy, Histology and Embryology, Semmelweis University, Budapest, Hungary
| | - Szilvia Oláh
- MTA-ELTE Laboratory of Molecular and Systems Neurobiology, Department of Physiology and Neurobiology, Institute of Biology, Eötvös Loránd University, Budapest, Hungary
| | - Dávid Keller
- Laboratory of Neuromorphology, Department of Anatomy, Histology and Embryology, Semmelweis University, Budapest, Hungary
| | - Rashmi Kumari
- MTA-ELTE Laboratory of Molecular and Systems Neurobiology, Department of Physiology and Neurobiology, Institute of Biology, Eötvös Loránd University, Budapest, Hungary
| | - Emese A. Fazekas
- MTA-ELTE Laboratory of Molecular and Systems Neurobiology, Department of Physiology and Neurobiology, Institute of Biology, Eötvös Loránd University, Budapest, Hungary
| | - Vivien Csikós
- MTA-ELTE Laboratory of Molecular and Systems Neurobiology, Department of Physiology and Neurobiology, Institute of Biology, Eötvös Loránd University, Budapest, Hungary
| | - Éva Renner
- Human Brain Tissue Bank and Microdissection Laboratory, Semmelweis University, Budapest, Hungary
| | - Melinda Cservenák
- MTA-ELTE Laboratory of Molecular and Systems Neurobiology, Department of Physiology and Neurobiology, Institute of Biology, Eötvös Loránd University, Budapest, Hungary
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Yamaguchi Y, Breves JP, Haws MC, Lerner DT, Grau EG, Seale AP. Acute salinity tolerance and the control of two prolactins and their receptors in the Nile tilapia (Oreochromis niloticus) and Mozambique tilapia (O. mossambicus): A comparative study. Gen Comp Endocrinol 2018; 257:168-176. [PMID: 28652133 PMCID: PMC5742082 DOI: 10.1016/j.ygcen.2017.06.018] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2017] [Revised: 05/16/2017] [Accepted: 06/21/2017] [Indexed: 12/15/2022]
Abstract
Osmoregulation in vertebrates is largely controlled by the neuroendocrine system. Prolactin (PRL) is critical for the survival of euryhaline teleosts in fresh water by promoting ion retention. In the euryhaline Mozambique tilapia (Oreochromis mossambicus), pituitary PRL cells release two PRL isoforms, PRL188 and PRL177, in response to a fall in extracellular osmolality. Both PRLs function via two PRL receptors (PRLRs) denoted PRLR1 and PRLR2. We conducted a comparative study using the Nile tilapia (O. niloticus), a close relative of Mozambique tilapia that is less tolerant to increases in environmental salinity, to investigate the regulation of PRLs and PRLRs upon acute hyperosmotic challenges in vivo and in vitro. We hypothesized that differences in the regulation of PRLs and PRLRs underlie the variation in salinity tolerance of tilapias within the genus Oreochromis. When transferred from fresh water to brackish water (20‰), Nile tilapia increased plasma osmolality and decreased circulating PRLs, especially PRL177, to a greater extent than Mozambique tilapia. In dispersed PRL cell incubations, the release of both PRLs was less sensitive to variations in medium osmolality in Nile tilapia than in Mozambique tilapia. By contrast, increases in pituitary and branchial prlr2 gene expression in response to a rise in extracellular osmolality were more pronounced in Nile tilapia relative to its congener, both in vitro and in vivo. Together, these results support the conclusion that inter-specific differences in salinity tolerance between the two tilapia congeners are tied, at least in part, to the distinct responses of both PRLs and their receptors to osmotic stimuli.
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Affiliation(s)
- Yoko Yamaguchi
- Hawai'i Institute of Marine Biology, University of Hawai'i at Mānoa, Kaneohe, HI 96744, USA; Department of Biological Science, Faculty of Life and Environmental Science, Shimane University, Matsue, Shimane 690-8504, Japan
| | - Jason P Breves
- Department of Biology, Skidmore College, Saratoga Springs, NY 12866, USA
| | - Maria C Haws
- Pacific Aquaculture and Coastal Resources Center, University of Hawai'i at Hilo, Hilo, HI 96720, USA
| | - Darren T Lerner
- Hawai'i Institute of Marine Biology, University of Hawai'i at Mānoa, Kaneohe, HI 96744, USA; Sea Grant College Program, University of Hawai'i at Mānoa, Honolulu, HI 96822, USA
| | - E Gordon Grau
- Hawai'i Institute of Marine Biology, University of Hawai'i at Mānoa, Kaneohe, HI 96744, USA
| | - Andre P Seale
- Hawai'i Institute of Marine Biology, University of Hawai'i at Mānoa, Kaneohe, HI 96744, USA; Department of Human Nutrition, Food and Animal Sciences, University of Hawai'i at Mānoa, Honolulu, HI 96822, USA.
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10
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Yamaguchi Y, Moriyama S, Lerner DT, Grau EG, Seale AP. Autocrine Positive Feedback Regulation of Prolactin Release From Tilapia Prolactin Cells and Its Modulation by Extracellular Osmolality. Endocrinology 2016; 157:3505-16. [PMID: 27379370 PMCID: PMC6285229 DOI: 10.1210/en.2015-1969] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 06/27/2016] [Indexed: 12/24/2022]
Abstract
Prolactin (PRL) is a vertebrate hormone with diverse actions in osmoregulation, metabolism, reproduction, and in growth and development. Osmoregulation is fundamental to maintaining the functional structure of the macromolecules that conduct the business of life. In teleost fish, PRL plays a critical role in osmoregulation in fresh water. Appropriately, PRL cells of the tilapia are directly osmosensitive, with PRL secretion increasing as extracellular osmolality falls. Using a model system that employs dispersed PRL cells from the euryhaline teleost fish, Oreochromis mossambicus, we investigated the autocrine regulation of PRL cell function. Unknown was whether these PRL cells might also be sensitive to autocrine feedback and whether possible autocrine regulation might interact with the well-established regulation by physiologically relevant changes in extracellular osmolality. In the cell-perfusion system, ovine PRL and two isoforms of tilapia PRL (tPRL), tPRL177 and tPRL188, stimulated the release of tPRLs from the dispersed PRL cells. These effects were significant within 5-10 minutes and lasted the entire course of exposure, ceasing within 5-10 minutes of removal of tested PRLs from the perifusion medium. The magnitude of response varied between tPRL177 and tPRL188 and was modulated by extracellular osmolality. On the other hand, the gene expression of tPRLs was mainly unchanged or suppressed by static incubations of PRL cells with added PRLs. By demonstrating the regulatory complexity driven by positive autocrine feedback and its interaction with osmotic stimuli, these findings expand upon the knowledge that pituitary PRL cells are regulated complexly through multiple factors and interactions.
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Affiliation(s)
- Yoko Yamaguchi
- Hawai'i Institute of Marine Biology (Y.Y., D.T.L., E.G.G., A.P.S.), University of Hawai'i at Mānoa, Kāne'ohe, Hawai'i 96744; School of Marine Biosciences (S.M.), Kitasato University, Minami-ku, Sagamihara, Kanagawa 252-0373, Japan; and University of Hawai'i Sea Grant College Program (D.T.L.) and Department of Human Nutrition, Food and Animal Sciences (A.P.S.), University of Hawai'i at Mānoa, Honolulu, Hawai'i 96822
| | - Shunsuke Moriyama
- Hawai'i Institute of Marine Biology (Y.Y., D.T.L., E.G.G., A.P.S.), University of Hawai'i at Mānoa, Kāne'ohe, Hawai'i 96744; School of Marine Biosciences (S.M.), Kitasato University, Minami-ku, Sagamihara, Kanagawa 252-0373, Japan; and University of Hawai'i Sea Grant College Program (D.T.L.) and Department of Human Nutrition, Food and Animal Sciences (A.P.S.), University of Hawai'i at Mānoa, Honolulu, Hawai'i 96822
| | - Darren T Lerner
- Hawai'i Institute of Marine Biology (Y.Y., D.T.L., E.G.G., A.P.S.), University of Hawai'i at Mānoa, Kāne'ohe, Hawai'i 96744; School of Marine Biosciences (S.M.), Kitasato University, Minami-ku, Sagamihara, Kanagawa 252-0373, Japan; and University of Hawai'i Sea Grant College Program (D.T.L.) and Department of Human Nutrition, Food and Animal Sciences (A.P.S.), University of Hawai'i at Mānoa, Honolulu, Hawai'i 96822
| | - E Gordon Grau
- Hawai'i Institute of Marine Biology (Y.Y., D.T.L., E.G.G., A.P.S.), University of Hawai'i at Mānoa, Kāne'ohe, Hawai'i 96744; School of Marine Biosciences (S.M.), Kitasato University, Minami-ku, Sagamihara, Kanagawa 252-0373, Japan; and University of Hawai'i Sea Grant College Program (D.T.L.) and Department of Human Nutrition, Food and Animal Sciences (A.P.S.), University of Hawai'i at Mānoa, Honolulu, Hawai'i 96822
| | - Andre P Seale
- Hawai'i Institute of Marine Biology (Y.Y., D.T.L., E.G.G., A.P.S.), University of Hawai'i at Mānoa, Kāne'ohe, Hawai'i 96744; School of Marine Biosciences (S.M.), Kitasato University, Minami-ku, Sagamihara, Kanagawa 252-0373, Japan; and University of Hawai'i Sea Grant College Program (D.T.L.) and Department of Human Nutrition, Food and Animal Sciences (A.P.S.), University of Hawai'i at Mānoa, Honolulu, Hawai'i 96822
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11
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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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12
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Seale AP, Yamaguchi Y, Johnstone WM, Borski RJ, Lerner DT, Grau EG. Endocrine regulation of prolactin cell function and modulation of osmoreception in the Mozambique tilapia. Gen Comp Endocrinol 2013; 192:191-203. [PMID: 23722201 DOI: 10.1016/j.ygcen.2013.05.011] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Revised: 05/11/2013] [Accepted: 05/14/2013] [Indexed: 01/06/2023]
Abstract
Prolactin (PRL) cells of the Mozambique tilapia, Oreochromis mossambicus, are osmoreceptors by virtue of their intrinsic osmosensitivity coupled with their ability to directly regulate hydromineral homeostasis through the actions of PRL. Layered upon this fundamental osmotic reflex is an array of endocrine control of PRL synthesis and secretion. Consistent with its role in fresh water (FW) osmoregulation, PRL release in tilapia increases as extracellular osmolality decreases. The hyposmotically-induced release of PRL can be enhanced or attenuated by a variety of hormones. Prolactin release has been shown to be stimulated by gonadotropin-releasing hormone (GnRH), 17-β-estradiol (E2), testosterone (T), thyrotropin-releasing hormone (TRH), atrial natriuretic peptide (ANP), brain-natriuretic peptide (BNP), C-type natriuretic peptide (CNP), ventricular natriuretic peptide (VNP), PRL-releasing peptide (PrRP), angiotensin II (ANG II), leptin, insulin-like growth factors (IGFs), ghrelin, and inhibited by somatostatin (SS), urotensin-II (U-II), dopamine, cortisol, ouabain and vasoactive intestinal peptide (VIP). This review is aimed at providing an overview of the hypothalamic and extra-hypothalamic hormones that regulate PRL release in euryhaline Mozambique tilapia, particularly in the context on how they may modulate osmoreception, and mediate the multifunctional actions of PRL. Also considered are the signal transduction pathways through which these secretagogues regulate PRL cell function.
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Affiliation(s)
- A P Seale
- Hawai'i Institute of Marine Biology, University of Hawaii, Kaneohe, HI 96744, USA.
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13
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Gardell AM, Yang J, Sacchi R, Fangue NA, Hammock BD, Kültz D. Tilapia (Oreochromis mossambicus) brain cells respond to hyperosmotic challenge by inducing myo-inositol biosynthesis. ACTA ACUST UNITED AC 2013; 216:4615-25. [PMID: 24072790 DOI: 10.1242/jeb.088906] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
This study aimed to determine the regulation of the de novo myo-inositol biosynthetic (MIB) pathway in Mozambique tilapia (Oreochromis mossambicus) brain following acute (25 ppt) and chronic (30, 60 and 90 ppt) salinity acclimations. The MIB pathway plays an important role in accumulating the compatible osmolyte, myo-inositol, in cells in response to hyperosmotic challenge and consists of two enzymes, myo-inositol phosphate synthase and inositol monophosphatase. In tilapia brain, MIB enzyme transcriptional regulation was found to robustly increase in a time (acute acclimation) or dose (chronic acclimation) dependent manner. Blood plasma osmolality and Na(+) and Cl(-) concentrations were also measured and significantly increased in response to both acute and chronic salinity challenges. Interestingly, highly significant positive correlations were found between MIB enzyme mRNA and blood plasma osmolality in both acute and chronic salinity acclimations. Additionally, a mass spectrometry assay was established and used to quantify total myo-inositol concentration in tilapia brain, which closely mirrored the hyperosmotic MIB pathway induction. Thus, myo-inositol is a major compatible osmolyte that is accumulated in brain cells when exposed to acute and chronic hyperosmotic challenge. These data show that the MIB pathway is highly induced in response to environmental salinity challenge in tilapia brain and that this induction is likely prompted by increases in blood plasma osmolality. Because the MIB pathway uses glucose-6-phosphate as a substrate and large amounts of myo-inositol are being synthesized, our data also illustrate that the MIB pathway likely contributes to the high energetic demand posed by salinity challenge.
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Affiliation(s)
- Alison M Gardell
- Department of Animal Science, University of California Davis, One Shields Avenue, Davis, CA 95616, USA
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14
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Abstract
Organisms exposed to altered salinity must be able to perceive osmolality change because metabolism has evolved to function optimally at specific intracellular ionic strength and composition. Such osmosensing comprises a complex physiological process involving many elements at organismal and cellular levels of organization. Input from numerous osmosensors is integrated to encode magnitude, direction, and ionic basis of osmolality change. This combinatorial nature of osmosensing is discussed with emphasis on fishes.
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Affiliation(s)
- Dietmar Kültz
- Department of Animal Science, Physiological Genomics Group, University of California, Davis, Davis, California
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15
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Seale AP, Watanabe S, Breves JP, Lerner DT, Kaneko T, Gordon Grau E. Differential regulation of TRPV4 mRNA levels by acclimation salinity and extracellular osmolality in euryhaline tilapia. Gen Comp Endocrinol 2012; 178:123-30. [PMID: 22569116 DOI: 10.1016/j.ygcen.2012.04.020] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Revised: 04/20/2012] [Accepted: 04/23/2012] [Indexed: 11/26/2022]
Abstract
Prolactin (PRL) cells of the euryhaline Mozambique tilapia, Oreochromis mossambicus, are osmoreceptors. Hyposmotically-induced PRL release is mediated by the inward movement of extracellular Ca(2+) through a stretch-activated Ca(2+) channel, which has been recently identified as the transient receptor potential vanilloid 4 (TRPV4). In the present study, changes in plasma PRL, as well as PRL and TRPV4 mRNA expression from the rostral pars distalis (RPD), were measured in fish transferred from seawater (SW) to fresh water (FW) and in fish transferred from FW to SW. The in vitro effects of osmolality on PRL release and on PRL and TRPV4 mRNA expression in dispersed PRL cells were compared between fish adapted to SW and FW. Both the release and expression of PRL fell when fish were transferred to SW and rose when fish were transferred to FW. By contrast, TRPV4 expression increased by 48h after fish were transferred from FW to SW and declined as early as 6h after transfer from SW to FW. A similar pattern was observed in vitro where TRPV4 expression responded positively to an increase in medium osmolality while PRL expression declined. Incubation with the Ca(2+) ionophore, A23187, and the phosphodiesterase inhibitor, IBMX, stimulated PRL release. While both IBMX and A23187 inhibited TRPV4 expression, only A23187 reduced PRL expression. Together, these findings indicate that the expression of TRPV4 mRNA is osmosensitive, increasing as extracellular osmolality rises. Furthermore, these data suggest that TRPV4 expression may be regulated through the same second messenger pathways involved in hyposmotically-induced PRL release.
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Affiliation(s)
- Andre P Seale
- Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, HI 96744, USA.
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16
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Seale AP, Watanabe S, Grau EG. Osmoreception: perspectives on signal transduction and environmental modulation. Gen Comp Endocrinol 2012; 176:354-60. [PMID: 22036842 DOI: 10.1016/j.ygcen.2011.10.005] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Revised: 10/05/2011] [Accepted: 10/12/2011] [Indexed: 01/16/2023]
Abstract
Osmoregulation is essential to life in vertebrates and osmoreception is a fundamental element in osmoregulation. Progress in characterizing the mechanisms that mediate osmoreception has been made possible by using a uniquely accessible cell model, the prolactin (PRL) cell of the euryhaline tilapia, Oreochromis mossambicus. In addition to a brief historical overview, we offer a summary of our recent progress on signal transduction and osmosensitivity in the tilapia PRL cell model. Prolactin is a central regulator of hydromineral balance in teleosts in freshwater (FW). Consistent with its essential role in FW osmoregulation, PRL release in tilapia is inversely related to extracellular osmolality, both in vivo and in vitro. Osmotically-driven changes in PRL cell volume control PRL release. A decrease in extracellular osmolality increases cell volume, leading to a rapid influx of Ca(2+) through stretch-activated channels followed by a sharp rise in PRL release. Our recent studies also suggest that cAMP is involved in the osmotic signal transduction, and that acclimation salinity can modulate PRL cell osmosensitivity. Prolactin cells from FW tilapia show a larger rise in PRL release after a reduction in medium osmolality than those from SW fish. Paradoxically, hyposmotically-induced increase in PRL mRNA was observed only in cells from SW fish. Our studies have revealed differences in the abundance of the water channel, aquaporin 3 (AQP3), and the stretch activated Ca(2+) channel, transient receptor potential vanilloid 4 (TRPV4) in PRL cells of FW and SW fish that may explain their differing osmosensitivity and osmoreceptive output in differing acclimation salinities.
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Affiliation(s)
- A P Seale
- Hawai'i Institute of Marine Biology, University of Hawaii, Kaneohe, HI 96744, USA.
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17
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Watanabe S, Seale AP, Grau EG, Kaneko T. Stretch-activated cation channel TRPV4 mediates hyposmotically induced prolactin release from prolactin cells of mozambique tilapia Oreochromis mossambicus. Am J Physiol Regul Integr Comp Physiol 2012; 302:R1004-11. [DOI: 10.1152/ajpregu.00632.2011] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In teleost fish, prolactin (PRL) is an important hormone for hyperosmoregulation. The release of PRL from the pituitary of Mozambique tilapia is stimulated by a decrease in extracellular osmolality. Previous studies have shown that hyposmotically induced PRL release is linked with cell volume changes, and that stretch-activated Ca2+ channels are likely responsible for the initiation of the signal transduction for PRL release. In this study, we identified the stretch-activated Ca2+ channel transient receptor potential vanilloid 4 (TRPV4) from the rostral pars distalis (RPD) of tilapia acclimated to freshwater (FW). TRPV4 transcripts were ubiquitously expressed in tilapia; the level of expression in RPDs of FW-acclimated fish was lower than that found in RPDs of seawater (SW)-acclimated fish. Immunohistochemical analysis of the pituitary revealed that TRPV4 is localized in the cell membrane of PRL cells of both FW and SW tilapia. A functional assay with CHO-K1 cells showed that tilapia TRPV4 responded to a decrease in extracellular osmolality, and that its function was suppressed by ruthenium red (RR) and activated by 4α-phorbol 12,13-didecanoate (4aPDD). Exposure of dissociated PRL cells from FW-acclimated tilapia to RR blocked hyposmolality induced PRL release. PRL release, on the other hand, was stimulated by 4aPDD. These results indicate that PRL release in response to physiologically relevant changes in extracellular osmolality is mediated by the osmotically sensitive TRPV4 cation channel.
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Affiliation(s)
- Soichi Watanabe
- Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, University of Tokyo, Bunkyo, Tokyo, Japan; and
| | - Andre P. Seale
- Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, Hawaii
| | - E. Gordon Grau
- Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, Hawaii
| | - Toyoji Kaneko
- Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, University of Tokyo, Bunkyo, Tokyo, Japan; and
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18
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19
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Xu S, Shimahara T, Cooke IM. Capacitance increases of dissociated tilapia prolactin cells in response to hyposmotic and depolarizing stimuli. Gen Comp Endocrinol 2011; 173:38-47. [PMID: 21549709 DOI: 10.1016/j.ygcen.2011.04.020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Revised: 04/07/2011] [Accepted: 04/19/2011] [Indexed: 11/25/2022]
Abstract
Prolactin (PRL) is the major hormonal mediator of adaptation to hyposmotic conditions. In tilapia (Oreochromis mossambicus), PRL cells are segregated to the rostral pars distalis of the anterior pituitary facilitating the nearly pure culture of dissociated PRL cells. Membrane capacitance (C(m)) was recorded at 1Hz or higher for tens of minutes as a surrogate monitor of PRL secretion by exocytosis from cells under perforated patch clamp. The study compares secretory responses to trains of depolarizing clamps (100 at 2.5 Hz, from -70 to +10 mV for 100 ms) to the physiological stimulus, exposure to hyposmotic medium, here a switch from 350 to 300 mOsm saline ([Ca²⁺] 15 mM). Two-thirds of cells tested with each stimulus responded. In response to depolarizing clamps, C(m) increased linearly at an average rate of 7.2 fF/s. The increase was also linear in response to hyposmotic perfusion, but the average rate was 0.68 fF/s. Response to depolarization was reversibly blocked in Ca²⁺-omitted saline, or in saline with 30 μM Cd²⁺. It was unaffected by 0.1 μM tetrodotoxin. By contrast, responses were reduced but not absent during perfusion of hyposmotic saline with Ca²⁺-omitted; 30 μM Cd²⁺ appeared to enhance the hyposmotic response. BAPTA-AM eliminated responses to both stimuli, confirming that secretion was dependent on increases of intracellular [Ca²⁺]. Together with previous observations from this laboratory of [Ca²⁺](i) with simultaneous collection and immunoassay of perfusate for PRL, we conclude that depolarization and hyposmotic stimuli initiate secretion by independent mechanisms.
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Affiliation(s)
- Shenghong Xu
- Békésy Laboratory of Neurobiology, University of Hawaii, Honolulu, HI 96822, USA
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20
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Kalamarz-Kubiak H, Gozdowska M, Nietrzeba M, Kulczykowska E. A novel approach to AVT and IT studies in fish brain and pituitary: in vitro perfusion technique. J Neurosci Methods 2011; 199:56-61. [PMID: 21569795 DOI: 10.1016/j.jneumeth.2011.04.035] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2011] [Revised: 04/06/2011] [Accepted: 04/26/2011] [Indexed: 12/22/2022]
Abstract
The study was designed to develop a new procedure for perfusion of brain and pituitary explants collected from three-spined stickleback (Gasterosteus aculeatus) and round goby (Neogobius melanostomus). The procedure was elaborated for studies of arginine vasotocin (AVT) and isotocin (IT) release from explants of both species. AVT and IT, analogs of mammalian vasopressin and oxytocin, are neurohormones produced in hypothalamus and released in neurohypophysis of Teleostei. Both nonapeptides are used as biomarkers of fish well being. Three perfusion sets were applied to test the method of medium transport into gradient container, without or with aeration. Medium supply to the gradient container from the top, without aeration is recommended only for short-term studies. Aeration of the medium with a mixture of 95% O(2) and 5% CO(2) at a pressure of 127.51 mm Hg is necessary for a long-term research. Transport of one or two media in the gradient container from the top and the bottom, simultaneously, requires aeration with a mixture of 95% O(2) and 5% CO(2) at a pressure of 315.03 mm Hg. Although the presented procedure has been elaborated for studies of AVT and IT in fish explants, after only minor modification, if any, it can serve many other purposes.
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Affiliation(s)
- Hanna Kalamarz-Kubiak
- Department of Genetics and Marine Biotechnology, Institute of Oceanology Polish Academy of Science, Powstańców Warszawy 55 Str., 81-712 Sopot, Poland.
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21
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Sato M, Nakakura T, Ogushi Y, Akabane G, Kurabuchi S, Suzuki M, Tanaka S. Expression of a mammalian aquaporin 3 homolog in the anterior pituitary gonadotrophs of the tree frog, Hyla japonica. Cell Tissue Res 2011; 343:595-603. [PMID: 21286755 DOI: 10.1007/s00441-010-1122-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Accepted: 12/10/2010] [Indexed: 11/29/2022]
Abstract
Aquaporins (AQPs) are a family of water channel proteins that play a major role in maintaining water homeostasis in various organisms. Several AQPs have been identified in the tree frog, Hyla japonica. Of these, AQP-h3BL, which is expressed in the basolateral membrane of the epithelial cells, is a homolog of mammalian AQP3. Using immunohistochemistry and in situ RT-PCR, we have demonstrated that AQP-h3BL is expressed in the anterior pituitary gonadotrophs of the tree frog but not in the other hormone-producing cells of the anterior pituitary. In gonadotrophs labeled for luteinizing hormone subunit-β (LHβ), AQP-h3BL protein was found to reside in the plasma membrane, the nuclear membrane and the cytoplasm. Double-labeling of AQP-h3BL mRNA and LHβ protein revealed that AQP-h3BL mRNA is expressed in the gonadotrophs. Following stimulation by gonadotropin-releasing hormone (GnRH), the label for AQP-h3BL localized in the plasma membrane became more intense, concomitant with the transport of LHβ-positive materials to the plasma membrane. These developments coincided with a decrease in the labeling density in the cytoplasm and near the nuclear membrane, suggesting that the latter localizations may function as "storage area" for AQP-h3BL. Immunoelectron microscopy also confirmed these localizations of AQP-h3BL protein. Based on these results, we suggest that AQP-h3BL protein in the frog gonadotrophs is involved in the formation of secretory granules, the swelling and increase in the volume of the granules and exocytosis.
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Affiliation(s)
- Megumi Sato
- Integrated Bioscience Section, Graduate School of Science and Technology, Shizuoka University, Ohya836, Suruga-ku, Shizuoka 422-8529, Japan
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22
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Watanabe S, Hirano T, Grau EG, Kaneko T. Osmosensitivity of prolactin cells is enhanced by the water channel aquaporin-3 in a euryhaline Mozambique tilapia (Oreochromis mossambicus). Am J Physiol Regul Integr Comp Physiol 2009; 296:R446-53. [DOI: 10.1152/ajpregu.90435.2008] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
In teleost fish, prolactin (PRL) has important actions in the regulation of salt and water balances in freshwater (FW) fish. Consistent with this role, the release of PRL from the pituitary of the Mozambique tilapia is stimulated as extracellular osmolality is reduced. Stretch-activated calcium-permeant ion channels appear to be responsible for the initiation of the signal transduction that leads to increased PRL release when PRL cells are exposed to reductions in extracellular osmolality. In this study, we examined a possible involvement of the aquaporin-3 (AQP3) water channel in this osmoreceptive mechanism in PRL cells of the tilapia. AQP3 expression levels in the rostral pars distalis of the pituitary, consisting predominantly of PRL cells, were higher in fish adapted to FW than in seawater (SW)-adapted fish. Immunohistochemical studies revealed that AQP3 is located in the cell membrane and perinuclear region of PRL cells, with more intense immunosignals in PRL cells of FW-adapted fish than in those of SW fish. In FW PRL cells, the magnitude of hyposmoticity-induced cell volume increase was greater than that seen in SW PRL cells. Mercury, a potent inhibitor of AQP3, inhibited hyposmoticity-induced cell volume increase and PRL release from FW PRL cells. The inhibitory effect of mercury was partially restored by β-mercaptoethanol, whereas no effect of mercury was observed on PRL release stimulated by a depolarizing concentration of KCl, which induces Ca2+influx and stimulates the subsequent Ca2+-signaling pathway. These results indicate significant contribution of AQP3 to osmoreception in PRL cells in FW-adapted tilapia.
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Kawauchi H, Sower SA, Moriyama S. Chapter 5 The Neuroendocrine Regulation of Prolactin and Somatolactin Secretion in Fish. FISH PHYSIOLOGY 2009. [DOI: 10.1016/s1546-5098(09)28005-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Kwong AKY, Ng AHY, Leung LY, Man AKY, Woo NYS. Effect of extracellular osmolality and ionic levels on pituitary prolactin release in euryhaline silver sea bream (Sparus sarba). Gen Comp Endocrinol 2009; 160:67-75. [PMID: 19027016 DOI: 10.1016/j.ygcen.2008.10.024] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2008] [Revised: 09/01/2008] [Accepted: 10/22/2008] [Indexed: 11/25/2022]
Abstract
In many euryhaline fish, prolactin (PRL) plays a key role in freshwater adaptation. Consistent with this function, the present study showed a remarkable reduction in pituitary PRL content of silver sea bream abruptly transferred to low salinity (6ppt). This reduction in pituitary PRL content followed closely the temporal changes in serum osmolality and ion levels. Serum osmolality, Na(+) and Cl(-) levels of silver sea bream abruptly transferred to hyposmotic salinity (6ppt) were markedly reduced 2h after the transfer. The decline in pituitary PRL content lagged behind the serum changes implying that reduction in pituitary PRL content is a response to the drop in serum ion levels and osmotic pressure. Silver sea bream pituitary cells were dispersed and exposed to a medium with reduced ion levels and osmolality in vitro, and PRL released from pituitary cells was significantly elevated. In hyposmotic exposed anterior pituitary cells, cell volume exhibited a 20% increase when exposed to a medium with a 20% decrease in osmolality. The enlarged pituitary cells did not shrink until the surrounding hyposmotic medium was replaced, a phenomenon suggesting an osmosensing ability of silver sea bream PRL cells for PRL secretion in response to a change in extracellular osmotic pressure. The decrease in pituitary PRL content in vivo and stimulated pituitary PRL release in vitro under reduced osmolality together suggest hyposmotic exposure triggers PRL release from the pituitary.
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Affiliation(s)
- Anna K Y Kwong
- Department of Biology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong Special Administrative Region, China
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Jorgacevski J, Stenovec M, Kreft M, Bajić A, Rituper B, Vardjan N, Stojilkovic S, Zorec R. Hypotonicity and peptide discharge from a single vesicle. Am J Physiol Cell Physiol 2008; 295:C624-31. [PMID: 18632733 PMCID: PMC2544434 DOI: 10.1152/ajpcell.00303.2008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2008] [Accepted: 07/11/2008] [Indexed: 11/22/2022]
Abstract
Neuroendocrine secretory vesicles discharge their cargo in response to a stimulus, but the nature of this event is poorly understood. We studied the release of the pituitary hormone prolactin by hypotonicity, because this hormone also contributes to osmoregulation. In perfused rat lactotrophs, hypotonicity resulted in a transient increase followed by a sustained depression of prolactin release, as monitored by radioimmunoassay. In single cells imaged by confocal microscopy, hypotonicity elicited discharge of the fluorescently labeled atrial natriuretic peptide cargo from approximately 2% of vesicles/cell. In contrast, KCl-induced depolarization resulted in a response of approximately 10% of vesicles/cell, with different unloading/loading time course of the two fluorescent probes. In cell-attached studies, discrete changes in membrane capacitance were recorded in both unstimulated and stimulated conditions, reflecting single vesicle fusion/fissions with the plasma membrane. In stimulated cells, the probability of occurrence of full fusion events was low and unchanged, whereas over 95% of fusion events were transient, with the open fusion pore probability, the average pore dwell-time, the frequency of occurrence, and the fusion pore conductance increased. Hypotonicity only rarely elicited new fusion events in silent membrane patches. The results indicate that, in hypotonicity-stimulated lactotrophs, transient vesicle fusion mediates hormone release.
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Affiliation(s)
- Jernej Jorgacevski
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
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Lee KM, Kaneko T, Katoh F, Aida K. Prolactin gene expression and gill chloride cell activity in fugu Takifugu rubripes exposed to a hypoosmotic environment. Gen Comp Endocrinol 2006; 149:285-93. [PMID: 16884723 DOI: 10.1016/j.ygcen.2006.06.009] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2006] [Revised: 06/15/2006] [Accepted: 06/18/2006] [Indexed: 11/15/2022]
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Boutet I, Long Ky CL, Bonhomme F. A transcriptomic approach of salinity response in the euryhaline teleost, Dicentrarchus labrax. Gene 2006; 379:40-50. [PMID: 16737785 DOI: 10.1016/j.gene.2006.04.011] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2005] [Revised: 04/11/2006] [Accepted: 04/17/2006] [Indexed: 11/23/2022]
Abstract
Euryhaline teleosts possess the capacity to osmoregulate under various environmental conditions (freshwater to hypersaline water). This physiological capacity is generally monitored using enzyme activity assays (Na+/K+ -ATPase...), hormones quantification (prolactine, growth hormone) or their mRNAs expression. To date, few studies addressed the genetic correlates of adaptation to varying salinity at a molecular level in such fish. In the sea bass Dicentrarchus labrax, genetic differentiation was observed at specific allozyme loci between lagoon- and open-sea populations. In the present study, we investigated transcriptomic response of D. labrax to salt- and freshwater acclimation in two organs involved in osmoregulation, gill and intestine. By using suppression subtractive hybridisation, we characterised 586 partial cDNA sequences encoding proteins potentially involved in the metabolism of sea bass acclimated to salt- or freshwater under experimental conditions. Using these results, we first characterised complete genomic sequence of a carbonic anhydrase and then analysed mRNA expression of genes potentially involved in osmoregulation mechanisms (Na+/K+ -ATPase, carbonic anhydrase, angiotensin-converting enzyme and claudin-3), cell-cycle regulation (secretagogin) and immune system (nephrosin) in gill and intestine of wild fish from open sea and lagoons. Our analyses indicate a strong tissue- and environmental-dependant expression pattern for all the genes studied. A transcriptomic approach such as described in the present paper provides thus a first description of genes involved in metabolic or structural functions important for coping with environmental salinity variations in a euryhaline fish like the common sea bass D. labrax. It should be supplemented by proteomics to check the direct involvement of the gene products at the protein level, and by polymorphism analyses if one is to understand population or individual fluctuations in acclimation to salinity variation.
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Affiliation(s)
- I Boutet
- UMR CNRS-IFREMER 5171 Génome, Populations, Interactions, Adaptation, Station Méditerranéenne de l'Environnement Littoral, 1 Quai de la Daurade, 34200 Sète, France.
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Liu NA, Liu Q, Wawrowsky K, Yang Z, Lin S, Melmed S. Prolactin Receptor Signaling Mediates the Osmotic Response of Embryonic Zebrafish Lactotrophs. Mol Endocrinol 2006; 20:871-80. [PMID: 16339273 DOI: 10.1210/me.2005-0403] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The pituitary hormone prolactin (PRL) regulates salt and water homeostasis by altering ion retention and water uptake through peripheral osmoregulatory organs. To understand the role of osmotic homeostasis in the development of PRL-secreting lactotrophs, we generated germline transgenic zebrafish coexpressing red fluorescent protein directed by Prolactin regulatory elements (PRL-RFP) and green fluorescent protein by the Pro-opiomelanocortin promoter (POMC-GFP). Transparent embryos expressing fluorescent markers specifically targeted to lactotrophs and corticotrophs, the two pituitary lineages involved in teleost osmotic adaptation, allowed in vivo dynamic tracing of pituitary ontogeny during altered environmental salinity. Physiological osmotic changes selectively regulate lactotroph but not corticotroph proliferation during early ontogeny. These changes are not suppressed by pharmacological dopamine receptor blockade but are completely abrogated by morpholino knockdown of the PRL receptor. PRL receptor signaling exerts robust effects on lactotroph development and plays a permissive role in lactotroph osmo-responsiveness, reflecting the dual peripheral and central interactions required for early pituitary development and embryonic homeostasis.
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MESH Headings
- Amino Acid Sequence
- Animals
- Animals, Genetically Modified
- Base Sequence
- DNA, Antisense/genetics
- Molecular Sequence Data
- Phylogeny
- Pituitary Gland, Anterior/embryology
- Pituitary Gland, Anterior/physiology
- RNA Interference
- Receptors, Dopamine/deficiency
- Receptors, Dopamine/genetics
- Receptors, Dopamine/physiology
- Receptors, Prolactin/deficiency
- Receptors, Prolactin/genetics
- Receptors, Prolactin/physiology
- Sequence Homology, Amino Acid
- Signal Transduction
- Water-Electrolyte Balance
- Zebrafish/embryology
- Zebrafish/genetics
- Zebrafish/physiology
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Affiliation(s)
- Ning-Ai Liu
- Department of Medicine, Cedars-Sinai Research Institute, University of California, Los Angeles, California 90048, USA
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Seale AP, Fiess JC, Hirano T, Cooke IM, Grau EG. Disparate release of prolactin and growth hormone from the tilapia pituitary in response to osmotic stimulation. Gen Comp Endocrinol 2006; 145:222-31. [PMID: 16242686 DOI: 10.1016/j.ygcen.2005.09.006] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2005] [Revised: 07/21/2005] [Accepted: 09/01/2005] [Indexed: 11/21/2022]
Abstract
In most teleost fishes, prolactin (PRL) plays a key role in freshwater (FW) adaptation, whereas growth hormone (GH) is involved in seawater (SW) adaptation in salmonids and certain euryhaline species including the tilapia, Oreochromis mossambicus. Consistent with its osmoregulatory activity, PRL release increases in response to physiologically relevant reductions in extracellular osmolality. When dispersed PRL and GH cells from FW-acclimatized fish were incubated in media of varying osmolalities, PRL release increased significantly in response to a 12% reduction in medium osmolality during 1 and 4h of exposure. By contrast, cells from SW-acclimatized fish responded only to a 24% reduction in osmolality. Growth hormone release on the other hand increased whether medium osmolality was reduced or raised. Cell volume increased together with PRL release during the perifusion of dispersed PRL cells in direct proportion to the reduction in medium osmolality. Growth hormone release increased whether GH cell volume increased or decreased. In in vivo studies, circulating PRL levels increased as early as 1h after the transfer of fish from SW to FW, whereas GH levels remained unchanged during 24h of acclimatization. These results indicate that while PRL and GH cells are osmosensitive, the PRL cells respond to reductions in extracellular osmolality in a manner that is consistent with PRL's physiological role in the tilapia. While the rise in GH release following the reduction in osmolality is of uncertain physiological significance, the rise in GH release with the elevation of medium osmolality may be connected to its role in SW adaptation.
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Affiliation(s)
- A P Seale
- Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, HI 96744, USA
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Watanabe S, Kaneko T, Aida K. Aquaporin-3 expressed in the basolateral membrane of gill chloride cells in Mozambique tilapia Oreochromis mossambicus adapted to freshwater and seawater. ACTA ACUST UNITED AC 2005; 208:2673-82. [PMID: 16000537 DOI: 10.1242/jeb.01684] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We have cloned a homologue of mammalian aquaporin-3 (AQP3) from gills of Mozambique tilapia using a reverse transcription-polymerase chain reaction (RT-PCR). The deduced amino acid sequence shared 64-75% homology with other vertebrate AQP3 homologues. RT-PCR revealed that tilapia AQP3 was expressed in the brain, pituitary, kidney, spleen, intestine, skin, eye and gill in tilapia adapted to freshwater (FW) and seawater (SW). We also examined functional characteristics of tilapia AQP3 using Xenopus oocytes as an in vitro transcribed cRNA expression system. Osmotic water permeability (Pf) of Xenopus oocytes expressing tilapia AQP3 was about 30-fold higher than that of control oocytes, and was 80% inhibited by treatment with 0.3 mmol l(-1) HgCl2. Light-microscopic immunocytochemistry of branchial epithelia revealed that tilapia AQP3 was expressed in gill chloride cells of FW- and SW-adapted tilapia. Electron-microscopic immunocytochemistry further demonstrated that tilapia AQP3 was localized in the basolateral membrane of gill chloride cells. Basolateral localization of AQP3 in gill chloride cells suggests that AQP3 is involved in regulatory volume changes and osmoreception, which could trigger functional differentiation of chloride cells.
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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.
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