Forskolin Stimulates Adenylate Cyclase Activity, Adenosine 3′,5′-Monophosphate Production and Peptide Release from the Intermediate Lobe of the Rat Pituitary Gland

Forskolin stimulates adenylate cyclase activity in a cell-free homogenate of the intermediate lobe (IL) of the rat pituitary gland. L-Isoproterenol, a beta-adrenergic agonist, enhances and apomorphine, a D-2 agonist, inhibits the forskolin-stimulated adenylate cyclase activity. Guanosine triphosphate is obligatory for the dopaminergic attenuation of the forskolin-enhanced enzyme activity. When tested upon enzymatically dispersed IL cells, forskolin enhances the release of both cAMP and immunoreactive alpha MSH-like peptides. These effects of forskolin upon the IL are discussed within the context of a previously published working hypothesis that cAMP in some way triggers the calcium-dependent release of hormones from the IL.