Oxygen tension profiles in isolated hamster retractor muscle at different temperatures.

Oxygen tension (P0(2)) profiles within unperfused hamster retractor muscles were obtained at 25, 30, and 37 degrees by using sharpened, recessed oxygen microelectrodes. The microelectrode was driven vertically into freshly excised muscle lying on a flat, impermeable boundary inside a diffusion chamber. Intramuscular P0(2) profiles were measured as a function of electrode depth in 10-mu m steps during both inward and outward penetrations when the upper surface of the muscles was exposed to humidified gases containing 10, 21, 50, and 100% 0(2). The ratio of the 0(2) consumption (M) to the 0(2) permeability (K, Krogh diffusion coefficient = D alpha, diffusion coefficient-solubility product) was estimated by curve-fitting the experimental steady-state distribution of 0(2) through muscles to the analytic solution of the diffusion equation assuming that M obeys zero-order kinetics and K is constant, uniform, and independent of P0(2). The ratios of M/K were independent of temperature and were found to be independent of surface P0(2) and muscle thickness. The average value of M/K was 3.9 +/- 0.45 (SE; n = 30) x 10(5) mm Hg/cm(2), which is consistent with that estimated from previous measurements of M and D using different non-steady-state techniques (Bentley et aL, 1993). These results are consistent with other in vitro 0(2) consumption measurements (Sullivan and Pittman, 1984) and do not provide evidence for nonclassical respiratory activity in resting mammalian skeletal muscle.