Atrial natriuretic peptide (ANP) exhibits a wide spectrum of cardiovascular, endocrine, metabolic and renal actions. cGMP is the major mediator of ANP at the cellular level and only tissues possessing paniculate guanylate cyclase appear to present ANP-induced actions. Three types of ANP receptors have recently been cloned. Two of them (A and B receptors) are homologous and contain guanylate cyclase catalytic domains. The C receptor could possibly regulate the metabolic fate of ANP. Data obtained by the radiation inactivation method suggest the presence of an inter- or intramolecular inhibitory component of nearly 90 kilodaltons that represses the catalytic activity of guanylate cyclase within its membrane environment. The mechanism of guanylate cyclase stimulation by ANP could involve this inhibitory component. Preliminary data suggest that the hyperresponsiveness of the particulate guanylate cyclase/cGMP system in hypertension occurs through modulation of the inhibitory component.