In vivo and in vitro effects of cholecystokinin octapeptide on the release of growth hormone in rats.
The effect of cholecystokinin octapeptide (CCK-8) on the release of growth hormone (GH) in rats was studied in vivo and in vitro. Intravenous injection of 5 micrograms/100 g BW of CCK-8 resulted in significant increase in the plasma GH level after 10 and 20 min. CCK-8 at concentrations of 10(-11)M to 10(-7)M also caused dose-dependent stimulation of GH release from dispersed cells of rat anterior pituitary. On the other hand, somatostatin (SRIF) inhibited GH release from dispersed cells of rat anterior pituitary in a dose-related manner at concentrations of 10(-7)M to 10(-9)M. Release of GH from the cells was increased by addition of K+ at high concentration (50 mM) in a Ca++-dependent manner. Addition of 10(-3)M verapamil to the incubation medium inhibited CCK-8-induced GH release from the cells. Addition of SRIF (10(-7)M) to the incubation medium inhibited GH release from the cells induced by CCK-8 or high K+ (50 mM). These results indicate that CCK-8 acts directly on the anterior pituitary cells to stimulate GH release and that calcium ion is involved in the mechanism of this effect.
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D010903:Pituitary Gland, Anterior / Q000187:drug effects* / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012844:Sincalide / Q000494:pharmacology*; D013004:Somatostatin / Q000494:pharmacology; D013997:Time Factors; D014700:Verapamil / Q000494:pharmacology
D013004:Somatostatin; D013006:Growth Hormone; D014700:Verapamil; D012844:Sincalide; D011188:Potassium; D002118:Calcium