INFLUENCE OF TEMPERATURE ON OXYGEN DIFFUSION IN HAMSTER RETRACTOR MUSCLE

A mathematical analysis by Popel et al. [Am. J. Physiol. 256 (Heart Ci rc. Physiol. 25): H921-H924, 1989] of in vivo data on arteriolar O-2 l oss suggested that Krogh's diffusion coefficient (KO2 = alpha . DO2, w here DO2 is the O-2 diffusion coefficient and alpha is the tissue O-2 solubility) in vivo could be an order of magnitude larger than that ca lculated from DO2 values measured in vitro at 22 degrees C and extrapo lated to 37 degrees C. In this study, to eliminate potential extrapola tion errors, we used a miniature hyperbaric chamber with 1-2 atm of O- 2 to maintain tissue oxygenation and allow DO2 measurements directly a t 37 degrees C while using a non-steady-state technique. The need for metabolic poisons that had been required by earlier experimental techn iques was thereby eliminated. DO2 measured directly at 37 degrees C (2 .42 . 10(-5) cm(2)/s) and the increase with temperature of DO2 between 30 and 41 degrees C (4.61%/degrees C) were unexpectedly higher than t he values we found at lower temperatures. Oxygen consumption was also higher than expected at 37 degrees and 40 degrees C. An analysis of th e activation energy for DO2 suggests that at higher temperatures there is a change in the diffusion pathway from that existing at lower temp eratures, perhaps caused by phase transitions in the lipid membranes.