Effects of Vasoactive Agents and Diuretics on Isolated Superfused Interlobar Renal Arteries

Abstract

Many diuretic agents alter renal blood flow by changing renal vascular resistance (1, 2 ) . However, little information is available concerning the actions of diuretics and other drugs on renal vascular smooth muscle, uncomplicated by reflex, hormonal or other extraneous influences. The purpose of this study therefore was to isolate a segment of the renal vascular tree for evaluation in vitro of direct actions of diuretics and other vasoactive agents. Renal arterioles constitute the major control of vascular resistance, however, the preafferent arteriolar portion of the renal vasculature accounts for a significant amount of the total resistance (3). For this reason, and because of the inaccessibility of the arterioles for work in vitro, int.erlobar renal arteries were chosen for study.Mcthods. Mongrel dogs weighing from 16 to 31 kg were anesthetized with pentobarbital sodium (30 mg/kg) and tracheotomized. Kidneys were approached by a retroperitone-a1 flank incision and quickly excised after clamping the vessels. The excised kidney was immediately immersed in a warmed (38') oxygenated (9 5 % 02-5 % COz) physiological