Respiration of Mitochondria of Red and White Skeletal Muscle.

BLANCHAER, M. C. Respiration of mitochondria of red and white skeletal muscle. Am. J. Physiol. 206(5) :1o15-1020. I g64.-Mitochondria of guinea pig red and white skeletal muscle were isolated in a medium containing 0.25 M sucrose, I mM ethylenediamine tetraacetate, and I y0 fraction V bovine albumin. Oxidative phosphorylation with pyruvate-malate as substrate was tightly coupled in both types of mitochondria when oxygen uptake was measured over a 2to +min period with a platinum electrode. The P/O ratios approached the theoretical value of 3. Oxygen consumption was also determined manometrically with the substrates IO mM pyruvate-1 mM malate, IO mM succinate, 6 mM reduced nicotinamide adenine dinucleotide (NADHZ), 20 mM dl-lactate, and 12-20 mM dl-a-glycerophosphate. White muscle mitochondria had a higher rate of oxygen consumption with cr-glycerophosphate than with lactate, succinate, and NADHZ. Those of red muscle were less active with cu-glycerophosphate than with the other substrates. These results indicate that an cr-glycerophosphate shuttle may couple the reactions generating NADHz in the cytoplasm of white muscle with the mitochondrial respiratory chain. The properties of the red muscle mitochondria suggest that the direct oxidation 01 mADH2 may be more important in this tissue than the a-glycerophosphate shuttle.