Which inhibits adenyl cyclase enzyme?: (A) Somatostatin, (B) Calcitonin, (C) Epinephrine, (D) Thyroxine
Answer is A. Somatostatin acts directly on the acid-producing parietal cells a G-protein coupled receptor which inhibits adenylate cyclase, thus effectively antagonising the stimulatory effect of histamine to reduce acid secretion.Ref: DM Vasudevan, 7th edition