Effects of cortisone, starvation, and rickets on oxidative enzyme activities of epiphyseal cartilage from rats.

Abstract Epiphyseal cartilage fractions from rats have been shown to have the enzymatic complement for oxidizing a wide variety of substrates though at relatively low rates compared to tissues such as liver and heart. In contrast to previous data for glycolytic enzymes, mitochondrial oxidative enzyme levels do not appear to be specifically affected by dietary rickets, starvation, or cortisone treatment and do not correlate with the oxidative activity of cartilage slices. These findings give added emphasis to our earlier suggestion that control of glycolytic enzyme levels plays a central role in regulation of cartilage cell economy. A marked difference in the relative distribution between supernatant and pellet fractions of glycerol-3- P oxidase compared to other typical mitochondrial enzymes including succinate dehydrogenase is interpreted as evidence for two classes of mitochondria in cartilage. According to this hypothesis, there is a class of more readily sedimented mitochondria which contain relatively much more glycerol-3- P oxidase. Although this enzyme is thought to play a role in regulation of glycolysis, the control of synthetic-degradative mechanisms for it does not appear to be coordinated with those for the glycolytic enzymes and glycerol-3- P dehydrogenase of the cartilage cytoplasm. It is suggested that the oxidase may have a special role in Ca 2+ accumulation by mitochondria.