Uridine diphosphoglucose dehydrogenase activity in normal and osteoarthritic human chondrocytes

The activity of uridine diphosphoglucose dehydrogenase (UDPGD), a key enzyme in the synthesis of proteoglycans was measured by a quantitative cytochemical method in normal and in osteoarthritic (OA) human cartilage. Normal adult chondrocytes showed low UDPGD activity, which was about half the activity of glucose-6-phosphate dehydrogenase of the same specimens. No significant increase in UDPGD activity was noted in OA chondrocytes. The lack of significantly enhanced UDPGD activity in OA indirectly agrees with studies showing normal 35S uptake in this disease and might explain in part the inability of chondrocytes to cope with continuous proteoglycan loss.