Abstract
Quantitative estimations indicate that the white muscle of the guinea pig has more than twice as much lactate and α-glycerophosphate dehydrogenase activity as red muscle and that both enzymes are largely cytoplasmic rather than particulate in distribution. In a related study it was shown that diametrically opposite conclusions can be drawn from the application of conventional histochemical methods to the same material. The discrepancy between the quantitative and histochemical findings appears to be due to the dependence of the histochemical methods upon local intracellular diaphorase activity. Low diaphorase levels in white muscle fibers produce the erroneous impression that the two dehydrogenases are also relatively inactive in these fibers. This artifact does not arise with α-glycerophosphate oxidase since it is not diaphorase-coupled. Quantitative determinations confirmed an earlier histochemical report that this enzyme is associated with particulate matter in muscle and is much more active in white than in red skeletal muscle fibers.