Redistribution of Renal Blood Flow Produced by Furosemide and Ethacrynic Acid

Abstract

Outer medullary blood flow (⁸⁵Kr method) is markedly reduced by furose-mide and ethacrynic acid injected into the renal artery of unanesthetized dogs; juxtamedullary cortical flow is also decreased. Anatomic localization of the redistribution was verified by autoradiography and by silastic injection studies. The injected specimens demonstrated a relative increase in the resistance of the peritubular capillaries of the juxtamedullary cortex and outer medulla, the blood supply of the juxtamedullary tubules, Henle's loops and collecting ducts; the vasa recta were dilated. Total renal blood flow (Doppler Flowmeter) decreased 10% 1 min after injection, and then gradually began to increase at 2 to 3 min, reaching levels 25 to 30% above control as cortical blood flow increased. The vasodilatation in the cortex is probably localized in the pars radiata. The onset of the diuresis coincided with the decrease in renal blood flow, and persisted after total renal blood flow returned to control value. Thus, the time course of the dicresis correlated more closely with the sustained decrease in juxtameduiary and outer medullary blood flow.