Effect of Dihydralazine on Plasma Renin Activity and Renal Function during Supine Exercise in Normal Subjects

Plasma renin activity, clearance of inulin (C in ) and para‐aminohippuric acid (C pah ), urinary sodium and potassium excretion during supine exercise were studied in normal healthy men. 8 subjects were treated during exercise with dihydralazine (Nepresolin® i.v.) and 8 subjects were untreated (control group). In the untreated subjects there was a statistically significant decrease in C pah and increase in filtration fraction. The decrease in C par during exercise was less in the dihydralazine‐treated group and the increase in filtration fraction almost inhibited. Urinary sodium excretion decreased significantly in both groups during exercise but returned slowly to pre‐exercise level in the dihydralazine group. Plasma renin activity increased during exercise in both groups, most markedly in the dihydralazine group. After exercise plasma renin activity decreased to pre‐exercise level in the control group but continued to increase in the dihydralazine group in spite of the increased renal blood flow. The findings indicate more marked sympathetic activity in the dihydralazine group and it is suggested that the sympathetic nervous system may have a direct influence on renin release irrespective of its renal hemodynamic action.