Acute Stimulated Hormone Release from Cultured GH3Pituitary Cells*

Abstract

Treatment of cultured rat pituitary GH3 cells with 50 mM KCl in growth medium released 33% of cell PRL [prolactin] and 18% of cell GH [growth hormone] with a half-time of 5 min. Hormone in the culture medium was increased 2- to 4-fold over unstimulated levels. The response required Ca; Ba and Sr, but not Mg, could substitute for Ca. Low temperature completely inhibited hormone release, which was also reduced significantly by inhibitors of energy metabolism and by nitrogen. This acute response was similar in ionic requirements, hormones released, and time course to the acute effect of TRH [thyroliberin]. Like K stimulation, TRH resulted in acute release of both PRL and GH [growth hormone]. This contrasts with the finding that chronic TRH treatmkent reduced GH synthesis in GH3 cells, After a 10 min preincubation with K, subsequent short incubations with K released little hormone unless the cells were allowed to recover by incubation in normal medium for at least 2 h. This acutely releasable hormone poll seems to be located in a membrane-bound subcellular fraction, since GH3 cells did not discharge the cytoplasmic marker enzyme, lactate dehydrogenase, during K-stimulated hormone release.