Thermal-induced changes in cell volume and hormone release in prolactin cells of Mozambique tilapia
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2021
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The multifunctional pituitary hormone prolactin (PRL), is critical for survival when fish acclimate to freshwater environments by stimulating ion retention, ion absorption, and water secretion. Due to the important role PRL plays in osmoreception, examining the effect of temperature on this fundamental process can offer insight into how natural, climate-change- driven, or controlled temperatures may alter a process that underlies salinity acclimation in fish. Consistent with their role in fresh water (FW)-acclimation, PRL cells of the euryhaline and eurythermal Mozambique tilapia (Oreochromis mossambicus), respond to a drop in osmolality with a short-term release of PRL. Hyposmotic-induced PRL release is triggered by an increase in cell volume that enables extracellular Ca2+ to enter the cell through the transient receptor potential vanilloid 4 (TRPV4), a stretch gated cation channel shown to be thermosensitive in some vertebrates. While the cell-volume-dependent secretory response of tilapia PRL cells to a hyposmotic stimulus is well established, the effects of temperature on PRL cells have not been characterized. PRL cells were dispersed from the rostral pars distalis (RPD) of Mozambique tilapia and incubated at 26 and 32 °C in isosmotic and hyposmotic media. A delayed rise in PRL release from dispersed PRL cells was observed in response to an increase in temperature while hyposmotic-induced PRL release occurred rapidly. When dispersed PRL cells were subjected to a temperature increase from 26 to 32 oC, ~50% of the total cells gradually increased in volume by ~8%; all cells were responsive to a hyposmotic stimulus (280 mOsm/kg), increasing in volume by ~20%. These findings indicate that thermal-induced PRL release may be mediated, at least in part, through a cell-volume-dependent mechanism, similar to how osmoreception is achieved. Moreover, a possible mechanism through which many of the functions of PRL are affected by temperature is proposed.
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Endocrinology, Cell volume, Mozambique tilapia, Prolactin, Temperature Acclimation
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55 pages
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