Association of the atrial natriuretic factor receptor with guanylate cyclase in solubilized rat glomerular membranes

The elution profile of solubilized rat glomerular membranes from a gel filtration column showed two peaks of 125I-ANF (atrial natriuretic factor) binding (367 +/- 21, 156 +/- 12 KDa). Over 85% of the total binding for the extract was in the 367 KDa peak. Guanylate cyclase activity was correlated with 125I-ANF specific binding. ANF activation of guanylate cyclase was also observed. As observed previously with particulate membrane, Scatchard-analysis of ANF binding data with the solubilized extract was consistent with a two-site model. Both affinities (Kd's), 4 pM and 1 nM, are within the range of blood concentrations reported for ANF. These observations suggest that most rat glomerular ANF receptors are large molecular complexes coupled with guanylate cyclase in the 300-350 KDa size range.