[Possible involvement of cyclic GMP (cGMP) in atrial natriuretic factor (ANF) induced natriuresis]

In order to clarify the mechanism of action of ANF on nephron, nephrogenous cGMP (NcGMP) was calculated. And the interrelationship between the changes in NcGMP, urinary sodium excretions or renal hemodynamics were investigated with direct intrarenal infusion of various doses of ANF. A small dose of ANF (0.03 micrograms/kg/min) increased sodium clearance (CNa) significantly without any appreciable changes in NcGMP, creatinine clearance (Ccr) or renal blood flow (RBF). A larger dose of ANF (0.1 or 0.3 micrograms/kg/min) significantly increased CNa, NcGMP, RBF and Ccr. A net increase in CNa (delta CNa) had a positive correlation with that in NcGMP (delta NcGMP), but the regression line did not pass through the zero point. These findings imply that a larger dose of ANF might effect on glomeruli and gene-rate cGMP to induce natriuresis by raising GFR. However natriuresis induces by a small dose of ANF considered to be caused by the other mechanisms, possibly by the direct or indirect effect of ANF on renal tubules.