Serotonin interferes with Ca2+ and PKC signaling to reduce gonadotropin-releasing hormone-stimulated GH secretion in goldfish pituitary cells

General and Comparative Endocrinology
Yi YuJohn P Chang

Abstract

In goldfish, two endogenous gonadotropin-releasing hormones (GnRH), salmon GnRH (sGnRH) and chicken GnRH-II (cGnRH-II), are thought to stimulate growth hormone (GH) release via protein kinase C (PKC) and subsequent increases in intracellular Ca(2+) levels ([Ca(2+)](i)). In contrast, the signaling mechanism for serotonin (5-HT) inhibition of GH secretion is still unknown. In this study, whether 5-HT inhibits GH release by actions at sites along the PKC and Ca(2+) signal transduction pathways leading to hormone release were examined in primary cultures of goldfish pituitary cells. Under static incubation and column perifusion conditions, 5-HT reduced basal, as well as sGnRH- and cGnRH-II-stimulated, GH secretion. 5-HT also suppressed GH responses to two PKC activators but had no effect on the GH-releasing action of the Ca(2+) ionophore ionomycin. Ca(2+)-imaging studies with identified somatotropes revealed that 5-HT did not alter basal [Ca(2+)](i) but attenuated the magnitude of the [Ca(2+)](i) responses to the two GnRHs. Prior treatment with 5-HT and cGnRH-II reduced the magnitude of the [Ca(2+)](i) responses induced by depolarizing levels of K(+). Similar inhibition, however, was not observed with prior treatment of 5-HT and sG...Continue Reading

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Citations

Sep 9, 2009·General and Comparative Endocrinology·Mark A Sheridan, Alison L Hagemeister
Jun 23, 2015·Frontiers in Neuroscience·Parvathy PrasadIshwar S Parhar
Feb 9, 2012·Experimental Biology and Medicine·Lloyd L Anderson, Colin G Scanes
Nov 18, 2016·Royal Society Open Science·Marco A VindasTore S Kristiansen

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