Cytochrome oxidase activity in bone tissue.

Cytochrome oxidase activity was studied in articular and epiphyseal cartilage, in bone tissue and in callus. Changes in the activity of the enzyme were observed after ischaemic condition. Activity was the highest in the epiphyseal cartilage while in the other structures it decreased in the order of articular cartilage, chondroid tissue, newly formed woven bone, connective tissue cells, immature, preexisting lamellar bone tissue. It is assumed that differences in enzyme activity are due to differences in metabolic rate. The higher the activity of a structure in the intact state, the more marked was its decrease upon ischaemia. This implies that cells of higher metabolic rate are more sensitive to ischaemia.