Inhibition of anterior pituitary prostaglandin-stimulated adenylyl cyclase activity by somatostatin

Abstract

Rat anterior pituitary gland adenylate cyclase activity is stimulated by prostaglandins [PG] with an order of potency of PGE1 .simeq. PGE2 > PGA1 .mchgt. PGB1 .simeq. PGF1.alpha. .simeq. PGF2.alpha. which is the same for cAMP accumulation and growth hormone release. Somatostatin inhibited PG-stimulated adenylate cyclase with 50% of maximal inhibition at 1.48 .times. 10-8 .+-. 0.27 .times. 10-8 M. GTP also stimulated adenylate cyclase activity at concentrations greater tahn 10-6 M but did not prevent inhibition by somatostatin. At least 1 action of somatostatin evidently is exerted directly on cAMP formation.