ABSTRACT
In cell-free preparations (washed 600 x g pellets) of human renal medulla, glucagon produced a dose-dependent stimulation of adenylate cyclase. The stimulation of renal medullary adenylate cyclase by saturating concentrations of glucagon was additive to the saturating doses of vasopressin. Furthermore, L-isoproterenol stimulated renal medullary adenylate cyclase in a dose-dependent manner, and this stimulation was blocked by DL-propranolol. Stimulation of the renal medullary adenylate cyclase by maximal doses of glucagon and L-isoproterenol was additive. DL-Propranolol did not inhibit stimulation of glucagon. Thus, the results indicate the existence of a specific adenylate cyclase that is responsive to glucagon--distinct from the isoproterenol-sensitive adenylate cyclase and the previously described vasopressin-sensitive adenylate cyclase in human renal medulla. We suggest that the renal tubular effect of glucagon may be mediated by glucagon-dependent cyclic-AMP production in renal tissue.
