Superoxide dismutase and catalase activities in the growth cartilage: relationship between oxidoreductase activity and chondrocyte maturation.

Superoxide dismutase (SOD) and catalase are enzymes that protect cells from radical attack. Catalase disproportionates hydrogen peroxide, and SOD is an oxidoreductase that serves to dismutate the superoxide anion. The objective of this communication was to measure the activity of these disproportionating enzymes in the chick tibial growth cartilage and to relate enzyme activity to chondrocyte maturation and tissue calcification. Analytic techniques were optimized for the measurement of both enzymes; particular care was taken to ensure that the values obtained were due to SOD and catalase, not to the presence of other oxidases or contaminants. Catalase and SOD had similar profiles of activity in cartilage. For both enzymes, the highest levels of activity were observed in premineralized cartilage; as chondrocytes matured there was a progressive decrease in the activity of SOD and catalase. Comparison of chondrocyte SOD activity with nonmineralizing tissues indicated that the activity of cultured cartilage cells was low. We also measured the SOD activity of avascular chondrodystrophic cartilage and found it to be less than that of proliferating cartilage. When cartilage was electrofocused, three SOD isozymes were detected. The pI of the major isozyme corresponded to the copper-zinc isoform. We suggest that the observed changes in enzymatic activity are dependent on a number of cartilage-specific factors that include the vascular supply, the local production of oxygen radicals by chondrocytes, and the oxidative state of the tissue.