Countercurrent diffusion in the renal cortex of the rabbit.

Abstract

SUMMARY. Evidence was obtained for countercurrent diffusion of 14 C-n-butanol in the rabbit renal cortex. After injection into the renal artery of perfused, isolated rabbit kidneys, concentrations of both 14 C-butanol and tritiated water in the initial samples collected from the renal venous outflow exceeded those of 125 I-albumin when the rate of perfusion was low. When flow was increased, the 125 I-albumin curve was shifted to earlier times relative to the other labels. These observations confirm the existence of arteriovenous diffusion of 14 C-butanol and tritiated water in the kidney. In a second set of experiments, u C-butanol and tritiated water were infused for 10 or 60 seconds into the renal arteries of anesthetized rabbits, and the kidneys were then removed and frozen in liquid nitrogen. Cores were cut from the kidney surface and sectioned in a cryostat, and the ratio of 14

Is the Distribution of Tissue pO2Homogeneous?

“…pO 2 measurements made with different techniques and in different tissues confirm the presence of the intravascular longitudinal pO 2 gradient from arterioles to capillaries (6,13). However, this gradient reverses in the venules as diffusion, anatomic pairing with countercurrent flows, and convective shunts transport some of the oxygen from the arterioles to the venules (7,8). Comparatively large oxygen gradients at the arteriolar and venular walls have been found and may be a mechanism whereby the higher blood pO 2 is reduced to a perivascular pO 2 level in close proximity of the overall average interstitial pO 2 .…”

Diffusive shunting of gases and other molecules in the renal vasculature: physiological and evolutionary significance

“…Effros et al (39) tested the hypothesis that lipid-soluble substances are able to diffuse from arteries to veins in the kidney. They reasoned that this phenomenon would be evinced by the appearance of lipid-soluble substances in the renal vein at an earlier time point than non-lipid-soluble substances after administration via the renal artery (39).…”

“…Effros et al (39) tested the hypothesis that lipid-soluble substances are able to diffuse from arteries to veins in the kidney. They reasoned that this phenomenon would be evinced by the appearance of lipid-soluble substances in the renal vein at an earlier time point than non-lipid-soluble substances after administration via the renal artery (39). In perfused isolated kidneys from rabbits, they observed greater concentrations of [ 14 C]butanol (lipid soluble) than 3 H 2 O and 125 I-labeled albumin (non-lipid soluble) in initial samples collected from venous outflow.…”