| Abstract: | 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. |
