RELATIONSHIP OF URINARY FUROSEMIDE EXCRETION RATE TO NATRIURETIC EFFECT IN EXPERIMENTAL AZOTEMIA

Abstract

The relationship of natriuretic effect and furosemide excretion was studied in normal and azotemic dogs. Graded azotemia was produced in dogs by bilateral uretero-venous shunts of varying duration. The shunts were subsequently opened and urine and blood samples were taken to measure inulin, furosemide and Na concentrations. Renal blood flow was measured by an electromagnetic flow probe. Two groups of dogs, control and experimental, were studied. The experimental group received a loading dose followed by a constant infusion of furosemide. This dose produced a natriuresis in nonazotemic normal dogs. The magnitude of this natriuresis correlated with furosemide excretion rate (P < .005) and not with the plasma concentration of the drug. Furosemide clearance and extraction were inversely correlated with blood urea N2. In the furosemide-treated group the augmentation of Na secretion was not impaired except at blood urea N2 concentrations of > 200 mg/dl (2 dogs). Thus the reduced clearance of furosemide may account in part for the high dose necessary. Further studies appear to be in order to clarify the relationship of the natriuretic response to furosemide to the rate of urinary excretion and plasma concentration of the drug.