Inhibition of pituitary adenylate cyclase by atrial natriuretic factor.

The effect of synthetic rat atrial natriuretic factor (ANF) on adenylate cyclase activity was studied in rat anterior and posterior pituitary homogenates. ANF (Arg 101-Tyr 126) inhibited adenylate cyclase activity in anterior and posterior pituitary homogenates in a concentration dependent manner. The maximum inhibitions observed were 42% in anterior pituitary with an apparent Ki of 10(-10) M, and 25% with an apparent Ki of 10(-11) M in posterior pituitary. Corticotropin-releasing factor (CRF), vasoactive intestinal peptide (VIP) and prostaglandins (PGE1) stimulated adenylate cyclase to various degrees in anterior pituitary homogenates and ANF inhibited the stimulatory effect of all these hormones. In addition ANF was also able to inhibit the stimulation exerted by NaF and forskolin which activate adenylate cyclase by receptor independent mechanism. Similarly, the stimulatory effects of N-Ethylcarboxamide adenosine (NECA), NaF and forskolin on adenylate cyclase in posterior pituitary homogenates were also inhibited by ANF. This is the first study demonstrating the inhibitory effect of ANF on pituitary adenylate cyclase.