Specific binding sites for atrial natriuretic peptide (ANP) in cultured mesenchymal nonmyocardial cells from rat heart.

Specific binding sites for atrial natriuretic peptide (ANP) were studied in cultured mesenchymal nonmyocardial cells (NMC) from rat heart. Binding study using 125I-labeled synthetic rat (r) ANP revealed the presence of a single class of high-affinity binding sites for rANP in cultured NMCs derived from both atria and ventricles; the apparent dissociation constant (Kd) was approximately 0.2 - 0.3 nM and the number of maximal binding sites was approximately 190,000 - 300,000 sites/cell. rANP significantly stimulated intracellular cGMP formation of cardiac NMCs in a dose-dependent manner (1.6 X 10(-8) M - 3.2 X 10(-7) M). rANP had no effect on synthesis of prostaglandin I2 by cultured cardiac NMCs. The physiological significance of ANP action on cardiac tissue remains to be determined.