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

The presence of a significant barrier at the level of the capillary to the diffusion of oxygen into tissue would have major significance in biology. The rete mirabile of the eel, an organ made up of alternately disposed arterial and venous capillaries, was used to study this question. The two capillary beds were perfused with albumin-containing Krebs-Ringer bicarbonate buffer in an uncoupled countercurrent fashion with equal flows, and the preparation was shielded from atmospheric oxygen with a polyvinylidene chloride fibs. A constant arterial infusion containing labeled albumin, inulin, and water, and an increased oxygen content, and a venous infusion containing a greatly reduced oxygen content were begun, and from the steady state response to these, capillary permeability-surface products were calculated. Approximately half the labeled water and one-third of the arterial minus venous oxygen increment emerged in the arterial outflow, whereas in the flow-limited case none would be expected. We calculated permeability values for the labeled tracers (albumin, inulin, and water), assuming a surface area of 1 cm'/mg, and found these not to be significantly different from those previously reported (Circ Res 41: 791-798, 1977). The permeability value for oxygen at 25°C was 11.8 ± 1.9 (SD) x 10~ cm/sec. The data indicate that the limiting effect of the capillary wall on oxygen transfer is of a magnitude that must be taken into account in describing the factors affecting the distribution of oxygen to tissues. Circ Re» 44: 498-503, 1979