Oxygen tension profiles in isolated hamster retractor muscle at different temperatures

Oxygen tension (PO₂) profiles within unperfused hamster retractor muscles were obtained at 25, 30, and 37° 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 PO₂ profiles were measured as a function of electrode depth in 10-μm 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% O₂. The ratio of the O₂ consumption (M) to the O₂ permeability (K, Krogh diffusion coefficient = Dα, diffusion coefficient-solubility product) was estimated by curve-fitting the experimental steady-state distribution of O₂ 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 PO₂. The ratios of M/K were independent of temperature and were found to be independent of surface PO₂ and muscle thickness. The average value of M/K was 3.9 ± 0.45 (SE; n = 30) x 10⁵ mm Hg/cm², 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 O₂ consumption measurements (Sullivan and Pittman, 1984) and do not provide evidence for nonclassical respiratory activity in resting mammalian skeletal muscle.