Atrial natriuretic peptide binding properties of purified rat glomerular membranes

125I-ANP (3-[125I] iodotyrosyl28) binding studies with purified rat glomerular membranes indicate two types of physiologically relevant hormonal receptors, Types I and II, Kd approximately 5 pM and approximately 2.5 nM, respectively. All preparations were essentially free of capsular and tubular contamination. Binding data indicated that Type I receptors were three times more concentrated than Type II receptors in purified membrane fractions. When purified membranes were cross-linked with 125I-rANP, using disuccinimidyl suberate and separated by SDS-PAGE, approximately 75- and approximately 140-kDa proteins were specifically labeled in a ratio of approximately 3:1, respectively. Thus, in purified renal glomerular membranes, Type I receptors with molecular weight of approximately 75-kDa appeared to predominate and would be detectably saturated at circulating ANP concentrations as low as 15 pg/ml. These findings could account for the exquisite sensitivity of natriuretic response to ANP.