Inhibition of GH1 rat pituitary tumor cell adenylyl cyclase activity by somatostatin.

Somatostatin inhibits basal and chlorpromazine stimulated adenylyl cyclase activity in homogenates of GH1 rat pituitary tumor cells. The Dtryp8-Dcys14 analogue is more potent than tyrosyl somatostatin as an inhibitor of both basal and chlorpromazine-stimulated adenylyl cyclase. Somatostatin had no effect on sodium fluoride or quanylyl-imidodiphosphate-stimulated cyclase in GH1 cell homogenates or on basal, epinephrine or prostaglandin E1 stimulated cyclase activity in sonicated BHK fibroblasts. These results indicate a specific effect of somatostatin to inhibit pituitary adenylyl cyclase activity.