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

Rat anterior pituitary gland adenylyl cyclase activity is stimulated by prostaglandins with an order of potency of PGE1 congruent to PGE2 greater than PGA1 much greater than PGB1 congruent to PGF1 alpha congruent to PGF2 alpha which is the same for cAMP accumulation and growth hormone release. Somatostatin inhibited prostaglandin-stimulated adenylyl cyclase with an ID50 of 1.48 X 10(-8) +/- 0.27 X 10(-8) M. GTP also stimulated adenylyl cyclase activity at concentrations greater than 10(-6) M but did not prevent inhibition by somatostatin. These results indicate that at least one action of somatostatin is exerted directly on cAMP formation.