Acute changes in plasma volume, renin activity, and free aldosterone levels in healthy subjects following Fursemide administration

Abstract

The effects of acute changes in plasma volume on renin release and plasma free aldosterone levels are not well understood. Our experiments demonstrate quantitative changes in the above-mentioned parameters following salt depletion. Plasma renin activity was assayed 10, 20, 60, and 120 min after the intravenous injection of Fursemide in healthy human subjects. Plasma free aldosterone levels and plasma volume were measured 60 and 120 min after injection. Plasma renin activity rose significantly after 10 min, as compared with control values, the highest values coinciding with peaks in urinary volume and sodium excretion as well as lowest urinary osmolality. The plasma aldosterone increase, moderate at 60 min, was significant at 120 min. Plasma volume measurements, 60 min after injection, decreased significantly, with a tendency to return to control values at 120 min. Plasma renin activity, measured by the new micromethod of Boucher at intervals of 2 to 70 min after the intravenous injection of Fursemide in rats, revealed, as in humans, a significant increase after 10 min. These data show that the increase in renin precedes that in aldosterone following the marked decrease in plasma volume due to acute diuresis and sodium loss.