Comparison of cholinergic inhibition and beta-adrenergic stimulation of adenylate cyclase from rat and guinea-pig hearts: Effects of guanine nucleotides and monovalent cations

Abstract 1. 1. Adenylate cyclase activities and the effects of isoproterenol (a β-adrenergic receptor agonist), carbachol (a cholinergic receptor agonist) and forskolin (a plant diterpene) were determined in homogenates and washed particulate fractions prepared from rat and guinea-pig hearts. 2. 2. Many interesting differences were noted in the stimulatory and inhibitory effects of isoproterenol and carbachol respectively on the heart enzyme. 3. 3. The likely significance of these results is presented.