Inhibition of gonadotropin-stimulated adenylate cyclase by dansyl-arginyl-(4'-ethyl)piperidine amide (DAPA).
Protease inhibitors are known to suppress basal, fluoride-, and hormone-stimulated adenylate cyclase activities. The thrombin inhibitor, dansyl-arginyl-(4'-ethyl)piperidine amide (DAPA), also specifically inhibits the binding of gonadotropins to their receptors. Our studies were undertaken to find a concentration of DAPA that would specifically inhibit gonadotropin-stimulated adenylate cyclase without significantly altering basal, fluoride-, isoproterenol-, or prostaglandin E1-stimulated cyclase. Basal adenylate cyclase activity was not inhibited by DAPA in either human chorionic gonadotropin (hCG)- or follicle-stimulating hormone (FSH)-responsive rat ovarian plasma membranes. Human chorionic gonadotropin-stimulated cyclase was completely inhibited by DAPA at a concentration of 2.96 mM; the ID50 was 1.32 mM. Follicle-stimulating hormone-stimulated cyclase was completely inhibited by a DAPA concentration of 4.44 mM, and the ID50 was 1.75 mM. Dansyl-arginyl-(4'-ethyl)piperidine amide (2.96 mM) inhibited isoproterenol-, prostaglandin E1-, and fluoride-stimulated cyclase in hCG-responsive membranes by 11%, 28%, and 35%, respectively. Dansyl-arginyl-(4'-ethyl)piperidine amide (4.44 mM) inhibited fluoride- and prostaglandin-stimulated cyclase in FSH-responsive membranes by 10% and 11%, respectively. The data show that appropriate concentrations of DAPA can antagonize gonadotropin-stimulated adenylate cyclase while only minimally affecting fluoride- and other receptor-activated cyclase activities.