The Effect of Furosemide on the Intrarenal Blood Flow Distribution in the Dog

Furosemide (40 μg/min) was perfused directly into the renal artery of dogs in whom the femoral blood pressure was reduced (80 mm Hg) by aortic clamping above the renal arteries. This maneuver, which does not influence the intrarenal blood flow distribution, produced significant decreases of the urine volume, natriuresis, Ccreat, and CPAH, and prevented the marked diuresis normally produced by furosemide. Therefore the chances that systemic physiological changes occurred, secondary to large fluid movements, were minimized. In those conditions, however, furosemide produced a significant increase of the urine output and sodium excretion in the experimental kidney whereas Ccreat and CPAH were not affected. The outer cortical blood flow rate (ml/100 g-min) was modified neither by aortic constriction (562 ± 68 versus 569 ± 83) nor by the subsequent administration of furosemide (424 ± 70). The blood flow rate of the outer medulla in these three conditions remained unchanged (147 ± 52 versus 171 ± 44 versus 159 ± 54). The initial distribution of the radioactivity in each compartment remained comparable in the three conditions. In parallel with the results from the krypton-85 disappearance curves, the autoradiograms, silicone rubber casts, and EPAH did not suggest any change in the renal blood flow distribution secondary to furosemide administration.