Oxidative enzyme metabolism in rabbit intrasynovial flexor tendons. I. Changes in enzyme activity of the tenocytes with age

Abstract

Clinically, the results of surgical repair to tendons within the digital canal are generally unsatisfactory. It is not known whether the tendon cells themselves have the capacity to effect repair, or whether dependence on surrounding tissues is necessary. Our lack of understanding of these problems is partly due to an inadequate knowledge of tendon metabolism. The activities of three oxidative enzymes, succinate dehydrogenase (citric acid cycle), glucose-6-phosphate dehydrogenase (pentose phosphate pathway), and lactate dehydrogenase (glycolysis), were measured in flexor tendons of young and adult rabbits. The same enzymes were also measured in rat liver for comparison. The results showed that adult tenocytes were entirely dependent on anaerobic metabolism for their energy supply, and that their biosynthetic capability for nucleic acid and fat production was extremely limited. In contrast, the synovium was more active metabolically, and might be expected to have a greater capability for repair following injury. Young rabbit tenocytes were somewhat more active metabolically, and showed some capacity for aerobic metabolism and production of cofactors for biosynthesis. Generally, however, rabbit tendon as a whole would appear to have only a limited ability for repair, based on its metabolic activity. There are areas of fibrous cartilage within the tendon which always occur at regions subject to particular stress. These regions were metabolically more active than the tendon itself.