EVIDENCE THAT ETHANOL INDUCES PROLACTIN SECRETION IN GH4C1 CELLS BY PRODUCING CELL SWELLING WITH RESULTANT CALCIUM INFLUX

Although acute exposure to ethanol has been reported to affect hormone secretion, the data are sometimes conflicting, and the mechanism of action of ethanol is unclear. We have examined in GH4C1cells the effect of isotonic ethanol on cell volume measured with a Coulter counter, the cytosolic Ca2+concentration ([Ca2+]i) monitored with fura-2, and PRL secretion analyzed in a perifusion system. Isotonic ethanol caused prompt cell swelling and an explosive rise in both [Ca2+]iand PRL secretion proportional to the concentration of ethanol between 5-120 mM. The increases in both [Ca2+]iand PRL secretion induced by 80 mM isotonic ethanol were essentially abolished by removal of medium Ca2+or by nifedipine; the nifedipine IC50was approximately 20 nM. Cell swelling induced by hyposmolarity or isotonic urea similarly increased both [Ca2+]iand PRL secretion. Hypertonic ethanol did not cause cell swelling and was ineffective in inducing an increase in either [Ca2+]ior PRL secretion. These data suggest that in GH4C1cells a major mechanism by which ethanol stimulates PRL secretion is to induce cell swelling, thus producing enhanced Ca2+influx through dihydropyridine-sensitive Ca2+channels. © 1990 by The Endocrine Society.