PMID: 2120879Aug 1, 1990Paper

Role of extracellular calcium and calmodulin in prolactin secretion induced by hyposmolarity, thyrotropin-releasing hormone, and high K+ in GH4C1 cells

Acta Endocrinologica
X B WangS McAdams

Abstract

The mechanism by which 30% medium hyposmolarity induces PRL secretion by GH4C1 cells was compared with that induced by 100 nmol/l TRH or 30 mmol/l K+. Removing medium Ca2+, blocking Ca2+ channels with 50 mumol/l verapamil, or inhibiting calmodulin activation with 20 mumol/l trifluoperazine, 10 mumol/l chlorpromazine or 10 mumol/l pimozide almost completely blocked hyposmolarity-induced secretion. The smooth muscle relaxant, W-7, which is believed relatively specific in inhibiting the Ca2(+)-calmodulin interaction, depressed hyposmolarity-induced PRL secretion in a dose-dependent manner (r = -0.991, p less than 0.01). The above drugs also blocked or decreased high K(+)-induced secretion, but had much less effect on TRH-induced secretion. Secretion induced by TRH, hyposmolarity, or high K+ was optimal at pH 7.3-7.65 and was significantly depressed at pH 6.0 or 8.0, indicating that release of hormone induced by all 3 stimuli is due to an active cell process requiring a physiologic extracellular pH and is not produced by nonspecific cell toxicity. The data suggest hyposmolarity and high K+ may share some similarities in their mechanism of stimulating secretion, which is different from that of TRH.

Citations

Sep 1, 1992·Molecular and Cellular Endocrinology·X WangM A Greer
Jan 1, 2010·Hormone Molecular Biology and Clinical Investigation·Marko A PopovicArturo E Gonzalez-Iglesias
Feb 11, 1998·Physiological Reviews·F LangD Häussinger
Oct 15, 1991·Biochemical and Biophysical Research Communications·X B WangS McAdams

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