Capillary limitation of oxygen distribution in the isolated rete mirabile of the eel (Anguilla anguilla).

Abstract

A significant barrier at the level of the capillary to diffusion of O2 into tissue would be significant in biology. The rete mirabile of the eel, an organ made up of alternately disposed arterial and venous capillaries, was studied. The 2 capillary beds were perfused with albumin-containing Krebs-Ringer HCO3 buffer in an uncoupled countercurrent with equal flows, and the preparation was shielded from atmospheric O2 with a polyvinylidene chloride film. A constant arterial infusion containing labeled albumin, inulin and H2O, and increased O2 content, and a venous infusion containing a greatly reduced O2 content were begun, and from the steady state response, capillary permeability-surface products were calculated. Approximately 1/2 the labeled water and 1/3 of the arterial minus venous O2 increment emerged in the arterial outflow, and in the flow-limited case none was expected. Permeability values for the labeled tracers (albumin, inulin and H2O), were calculated assuming a surface area of 1 cm2/mg, and these were not significantly different from those previously reported. The permeability value for O2 at 25.degree. C was 11.8 .+-. 1.9 (SD) .times. 10-5 cm/s. The limiting effect of the capillary wall on O2 transfer must be accounted for in describing the factors affecting the O2 distribution to tissues.