Urinary angiotensin excretion during sodium restriction and diuretics.

The urinary excretion rate and plasma concentration of angiotensin I (UAI, PAI) and angiotensin II (UAII, PAII), and plasma renin activity (PRA) were measured in seven healthy volunteers in the supine and upright position both on free and restricted sodium intakes. The same variables were measured before and after intravenous injection of furosemide, as well as before and during intravenous infusion of chlorothiazide. Assumption of the upright posture as well as sodium restriction increased PAI, PAII, and PRA, but UAI and UAII excretion were not altered by these manoeuvres. Furosemide injection resulted in increases of all variables, albeit that PAI and PAII were elevated to a lesser extent then PRA. Chlorothiazide infusion caused a reduction in PAI, PAII, and PRA, whereas UAI and UAII excretion increased modestly. The discrepancies between changes in plasma and urinary AI and AII may indicate that urinary angiotensin excretion provides information which is supplementary to that of plasma angiotensins.