Receptor Regulation of Atrial Natriuretic Factor

Two atrial natriuretic factor (ANF) receptor subtypes are present in vascular nooth muscle cells: the B receptors (or biologically active) coupled to a guanylate cyclase ad the C receptors (clearance) representing 95% of the total number of ANF binding sites but noncoupled to a guanylate cyclase. Using binding experiments with 125I-ANF and measurement of cGMP production stimulated by ANF, we were able to demonstrate that ANF receptors are sensitive to homologous (induced by ANF) and heterologous regulation (induced by angiotensin II, All) in rat cultured vascular smooth muscle cells. The effect of the two hormones showed marked differences, in their time course, their reversibility and their consequence on guanylate cyclase activity. Although both ANF and All reduced the total umber of ANF binding sites after 18 h, ANF induced a desensitization of the guanylate cyclase whereas All elicited a potentialization of this system. From these results, we have included that in vascular cells B receptors are sensitive to homologous regulation and C receptors are sensitive to heterologous regulation by All. This also highlights a specific interaction between ANF and All at the receptor level.