Oxidative enzyme systems in ossifying cartilage

Abstract

Calcifying cartilage possesses both dehydro-genase and cytochrome oxidase systems, present predominantly in the hypertrophic cells. Ossifying cartilage shows a much greater respiratory activity than has been reported for non-ossifying articular cartilage. The respiration is cyanide-sensitive. The respiration of cartilage was stimulated by citrate, [alpha]-oxoglutarate, succinate, malate and pyruvate. It was inhibited by arsenite in the presence of citrate or [alpha]-oxoglutarate and by malonate in the presence of succinate. The synthesis of adenosine triphosphate in vivo, measured by incorporation of p32, is inhibited by 2:4-dinitrophenol; uptake of isotope into the bone salt was inhibited only after longer treatment with dinitrophenol. The possible significance of oxidative phosphorylation in calcification has been discussed.