Stimulation of guanylate cyclase activity by irreversible binding of atrial natriuretic peptide to its receptor

Abstract We examined receptor binding profiles of atrial natriuretic peptide (ANP) in rat tissue using 125 I-labeled α-rat ANP ([ 125 I]α-rANP). Specific [ 125 I]α-rANP binding to its receptor was reversible following addition of unlabeled free α-rANP, but it became increasingly irreversible with time during incubation. Irreversible binding of α-rANP was observed both at 0° and 25° in homogenates of adrenal capsules and lungs, crude membranes of renal glomeruli, partially purified membranes of lung, solubilized membrane preparations from renal glomeruli, and intact renal glomeruli. Irreversible binding increased in a time- and temperature-dependent manner. HPLC analysis demonstrated that the irreversibly bound radioactivity, which was extracted by 1 N CH 3 COOH from both intact renal glomeruli and from partially purified membranes, was associated with intact [ 125 I]α-rANP. Irreversibly bound α-rANP increased cGMP concentrations by activating guanylate cyclase activity. These findings suggest that the appearance of irreversible binding of α-rANP to its receptor is independent of its internalization, and may be involved in message transduction and subsequent biological responses.