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Osmoreception: perspectives on signal transduction and environmental modulation
A P Seale1, S Watanabe, E G Grau
1Hawai'i Institute of Marine Biology, University of Hawaii, Kaneohe, HI 96744, USA. seale@hawaii.edu
General and Comparative Endocrinology
|November 1, 2011
Summary
Osmoreception in tilapia prolactin (PRL) cells is key to vertebrate osmoregulation. Studies reveal how changes in cell volume and ion channels like TRPV4 mediate PRL release in response to varying salinities.
Area of Science:
- Comparative physiology
- Cellular biology
- Endocrinology
Background:
- Osmoregulation is vital for vertebrate survival.
- Osmoreception, the ability to sense osmotic pressure, is a critical component of osmoregulation.
- The prolactin (PRL) cell of the euryhaline tilapia (Oreochromis mossambicus) serves as a model for studying osmoreception mechanisms.
Purpose of the Study:
- To investigate the mechanisms of signal transduction and osmosensitivity in tilapia PRL cells.
- To understand how acclimation salinity affects PRL cell osmosensitivity and osmoreceptive output.
Main Methods:
- Utilized the tilapia PRL cell model for in vivo and in vitro studies.
- Examined osmotically-driven changes in PRL cell volume and calcium influx.
- Investigated the role of cAMP in osmotic signal transduction.
- Analyzed the abundance of aquaporin 3 (AQP3) and transient receptor potential vanilloid 4 (TRPV4) in PRL cells from fish acclimated to different salinities.
Main Results:
- PRL release is inversely related to extracellular osmolality in tilapia.
- Decreased extracellular osmolality increases tilapia PRL cell volume, leading to Ca(2+) influx and increased PRL release via stretch-activated channels.
- cAMP signaling is implicated in osmotic signal transduction.
- Tilapia PRL cells from freshwater (FW) fish exhibit greater PRL release upon hyposmotic challenge compared to saltwater (SW) fish.
- Hyposmotic induction of PRL mRNA was observed only in SW fish PRL cells.
- Differences in AQP3 and TRPV4 abundance in FW vs. SW tilapia PRL cells were identified, potentially explaining differential osmosensitivity.
Conclusions:
- Tilapia PRL cells effectively sense and respond to changes in extracellular osmolality.
- Acclimation salinity modulates PRL cell osmosensitivity, with FW fish cells showing a more robust response to hyposmotic conditions.
- Differential expression of AQP3 and TRPV4 may underlie the observed variations in osmosensitivity and osmoreceptive output between FW and SW tilapia.
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