Stimulation of human cardiac adenylate cyclase by vanadate

Experiments have been carried out to characterize the influence of the positive inotropic trace element vanadium (used as Na3VO4) on beta-adrenergic receptor coupled adenylate cyclase activity from human myocardium. Na3VO4 (10(4)M) stimulates basal activity as well as isoprenaline (10 microM)- and Mg2+ (20 mM) activated enzyme activity 1.5-2.4-fold. In contrast, adenylate cyclase activity in the presence of maximally activating concentrations of Gpp(NH)p (10 microM) cannot be further increased by Na3VO4. The results confirm the assumption (5) that vanadate stimulates adenylate cyclase by interacting with the nucleotide-binding site of this enzyme.