Cellular enzymatic activities in the articular cartilage of osteoarthritic and osteoporotic hip joints of humans: a quantitative cytochemical study.

Quantitative cytochemical methods were applied to measure the activity of several oxidative enzymes in human articular cartilage of the femoral head obtained from osteoarthritic patients (OA) and from patients with fractured femoral neck (OP) due to primary osteoporosis. In both conditions, lactate dehydrogenase (LDH) was found to be the most active one followed by two additional cytosolic enzymes: glyceraldehyde 3-phosphate dehydrogenase (GAPD) and glucose 6-phosphate dehydrogenase (G6PD). On the other hand, the activity of mitochondrial enzymes such as succinate dehydrogenase (SDH) and beta-hydroxyacyl dehydrogenase (HOAD), appeared much lower in degree. Except for HOAD, all the other enzymes exhibited a high degree of activity along the inner zone in the cartilage, i.e., zone 3b, indicative of an apparently more active metabolism in the osteochondral junction. G6PD activity was significantly higher (p less than 0.01) in OP than in OA patients. By contrast, SDH appeared more active in specimens obtained from OA patients. The remaining enzymes showed no appreciable activity differences between cartilages of OP and OA patients. These findings suggest that oxidative enzyme activity in chondrocytes involved in osteoarthritis does not differ substantially from that in cartilage of OP patients.