Sodium deprivation and renin secretion in unanesthetized dogs

Abstract

Plasma renin activity was measured in unanesthetized dogs during daily ingestion of 60 (control) and 10 (low Na) mEq Na/day. The renin method was validated by a study of angiotensinogen and in vitro angiotensin generation. Control renin was 2.4[plus or minus] 0.3 (mean [plus or minus] SE) ng angiotensin equivalents/ml plasma. Twenty-four hours after beginning the low-Na diet, arterial renin increased significantly by 1.9 [plus or minus] 0.5 (P< .001), and remained elevated throughout the low Na period (up to 22 days), returning to normal within 48 hr. after reinstituting the control diet. During Na deprivation, no significant changes of the following parameters were observed: arterial mean and pulsatile blood pressure, heart rate, plasma Na and K, PAH [para-amino hippurate] and creatinine clearances. Surgical renal denervation slowed the renin response to Na deprivation but did not abolish it. Acute pharmacological gan-glionic, alpha receptor, and beta receptor blockade had no effect upon levels of plasma renin during ingestion of control or low-Na diets. The increased renin secretioninduced by dietary Na deprivation is not primarily mediated by the sympathetic nervous system.