Sodium intake influences the effects of atriopeptin on blood pressure and transcapillary fluid shift in the rat.

The influence of chronic changes in sodium intake on the acute effects of atrial natriuretic peptide (ANP) on arterial pressure and fluid translocation was assessed in acutely binephrectomized rats. After 3 weeks of either low sodium or high sodium diet, animals were administered ANP at doses of 0.1 and 1 microgram/kg/min. A marked and irreversible hypotensive response to ANP was observed with the higher infusion rate in the low sodium group, whereas blood pressure did not change significantly in the other groups. The effect of ANP on plasma protein concentration was less marked than that on hematocrit in all groups and was not significantly affected by sodium intake. The effect of both doses of ANP on hematocrit was enhanced in the high sodium group, indicating that the fluid shift out of the intravascular compartment was magnified by high sodium intake.