OXYGEN-TENSION PROFILES IN ISOLATED HAMSTER RETRACTOR MUSCLE AT DIFFERENT TEMPERATURES

Oxygen tension (PO2) profiles within unperfused hamster retractor musc les were obtained at 25, 30, and 37 degrees by using sharpened, recess ed oxygen microelectrodes. The microelectrode was driven vertically in to freshly excised muscle lying on a flat, impermeable boundary inside a diffusion chamber. Intramuscular PO2 profiles were measured as a fu nction of electrode depth in 10-mu m steps during both inward and outw ard penetrations when the upper surface of the muscles was exposed to humidified gases containing 10, 21, 50, and 100% O-2, The ratio of the O-2 consumption (M) to the O-2 permeability (K, Krogh diffusion coeff icient = D alpha, diffusion coefficient-solubility product) was estima ted by curve-fitting the experimental steady-state distribution of O-2 through muscles to the analytic solution of the diffusion equation as suming that M obeys zero-order kinetics and K is constant, uniform, an d independent of PO2. The ratios of M/K were independent of temperatur e 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 10(5) mm Hg /cm(2), which is consistent with that estimated from previous measurem ents of M and D using different nonsteady-state techniques (Bentley et al., 1993). These results are consistent with other in vitro O-2 cons umption measurements (Sullivan and Pittman, 1984) and do not provide e vidence for nonclassical respiratory activity in resting mammalian ske letal muscle. (C) 1996 Academic Press, Inc.