Temperature modulates the osmosensitivity of tilapia prolactin cells

Area of Science:

• Comparative Physiology
• Endocrinology
• Environmental Adaptation

Background:

• Prolactin (Prl) is crucial for freshwater acclimation in euryhaline fish.
• Prl cells in Mozambique tilapia (Oreochromis mossambicus) function as osmoreceptors and are thermosensitive.
• Understanding temperature's effect on osmoreception is key to fish adaptation.

Purpose of the Study:

• To investigate how temperature influences osmoreception in tilapia Prl cells.
• To examine the combined effects of temperature and salinity on Prl release and gene expression.

Main Methods:

• Tilapia Prl cells, acclimated to freshwater (FW) or seawater (SW), were incubated under varied temperatures (20, 26, 32°C) and osmolalities (280, 330, 420 mOsm/kg).
• Measured Prl isoform (Prl188, Prl177) release, mRNA expression of Prl isoforms, Prl receptors (prlr1, prlr2), and TRPV4 channels.
• Analyzed the expression of key transcription factors regulating Prl.

Main Results:

• Prl release increased with hyposmolality and higher temperatures; Prl188 release was suppressed at 20°C.
• In SW fish, prl188 mRNA increased with temperature (low osmolality), while prl177 decreased (high temp/osmolality).
• SW fish showed decreased prlr1, prlr2, trpv4, and transcription factor expression at 32°C, indicating compensatory mechanisms.

Conclusions:

• Temperature modulates osmoreception in tilapia Prl cells.
• Thermal and osmotic responses are dependent on acclimation salinity.
• Cellular mechanisms exist to compensate for temperature-induced changes in Prl release.