NTP pyrophosphohydrolase in human chondrocalcinotic and osteoarthritic cartilage. II. Further studies on histologic and subcellular distribution.

A nucleoside triphosphate (NTP) pyrophosphohydrolase was previously demonstrated in human chondrocalcinotic and osteoarthritic articular cartilage. In this study, grinding and enzymatic techniques for cartilage subcellular fractionation were compared. It was shown that this enzyme was concentrated in fractions enriched in plasma membranes. The enzyme had the same activity in cartilage slices as in triton X-100 extracts, and all of the activity was removed by preliminary treatment of cartilage slices with pronase. Histologic separation of cartilages into tangential and upper radial versus lower radial zones indicated no difference in concentrations of this enzyme. A role is postulated for this enzyme in metabolic chondrocytic plasma membrane responses to injury or destabilization from other causes, such as rapid synthesis or cell division.