Specificity of a porcine 127-kd nucleotide pyrophosphohydrolase for articular tissues

Objective. To determine the tissue specificity of a porcine 127-kd nucleotide pyrophosphohydrolase (NTPPHase) found in vesicles derived from hyaline articular cartilage (ACV). Methods. Homogenates of porcine brain, lung, liver, kidney, urinary bladder, pancreas, spleen, skin, vena cava, marrow, bone (cells), tendon (Achilles), ligament (anterior cruciate), elastic cartilage, meniscus, and hyaline cartilage were analyzed for NTPPHase activity (thymidine monophosphate paranitrophenyl ester substrate) and by Western blot using polyclonal antibodies against 127-kd NTPPHase and against recombinant PC-1, another ecto-NTPPHase. Results. All tissues contained NTPPHase activity; the highest specific activity was found in hyaline articular cartilage, the lowest in brain, ACV-associated 127-kd NTPPHase was expressed in cartilage, ligament, and tendon. PC-1 was also expressed in those tissues and in skin, kidney, bone cells, and (probably) in liver and muscle. Conclusion. The 127-kd NTPPHase appears to be highly specific for articular tissues.