INTERACTION OF ATRIAL-NATRIURETIC-PEPTIDE WITH ITS RECEPTORS IN BOVINE LUNG MEMBRANES

In bovine lung membranes, atrial natriuretic peptide (ANP) showed temperature-dependent binding to guanylate cyclase-natriuretic peptide receptor (NPR-GC). Photoaffinity labeling of the receptors with 4-azidobenzoyl (AZB)-I-125-ANP and competitive binding studies with I-125-ANP, ANP and atriopeptin I (API) revealed that NPR-GC was detected as the predominant ANP-binding protein at 0 degrees C, whereas at 37 degrees C natriuretic peptide clearance receptor (NPR-C) was detected as the predominant protein. The ratio of NPR-GC and NPR-C was 89:11 at 0 degrees C for 40 min, respectively, whereas 6:94 at 37 degrees C, AZB-I-125-ANP bound to NPR-GC dissociated from the binding site within 5 min at 37 degrees C but not at 6 degrees C, whereas ANP bound to NPR-C did not dissociate from the binding site at 0 and 37 degrees C, The dissociated AZB-I-125-ANP rapidly rebound to NPR-GC at 37 degrees C but not to NPR-C, and the dissociated NPR-GC was capable of binding. Some AZB-I-125-ANP was hydrolyzed by a membrane-bound proteinase(s). Phosphoramidon inhibited the hydrolysis of AZB-I-125-ANP, Thus, the dissociated AZB-I-125-ANP rebound to NPR-GC and NPR-C. These results suggest that usually intact ANP repeatedly binds to NPR-GC until hydrolysis, Furthermore, the majority of ANP bind to NPR-GC before binding to NPR-C under physiological temperature.