Abstract
Elevated levels of nucleoside triphosphate pyrophosphohydrolase (ENP) (NTP→NMP+PPi) are present in cartilage extracts of patients with calcium pyrophosphate (PPi) crystal deposition disease (CPPD) (Tenenbaum, Arth Rheum 24:492, 1981).
PPi is generated from 1 mM ATP in dog articular cartilage organ culture (800 ± 300 pmol/hr/mg wet wt, n=11. The specific activity of (32P)PPi produced from 1 mM gamma-(32P)ATP is 97% that of the labeled ATP. AMPCP, EHNA, and dipyridamole do not alter PPi generation in this system. No PPi is generated when adenosine, AMP or ADP are substituted for ATP.
ENP activities on cultured human skin fibroblasts from 24 CPPD subjects are elevated compared to 13 oestoarthritic and 7 normal controls (p<0.002, Wilcoxon's rank sum) with higher values for 13 sporadic compare to 11 familial cases of CPPD. No differences exist for ecto-5'nucleotidase or pyrophosphatase. Intracellular PPi is higher for CPPD fibroblasts (p<0.0002) and correlates with ENP activity (rs=0.49, <p.0.05, Spearman's rank correlate).
These data demonstrate the in vitro generation of PPi in cartilage in the presence of ATP is entirely due to ENP activity. The expression and variation of ENP activity and intracellular PPi levels in nonarticular human cells support the hypothesis of a generalized metabolic defect in CPPD.
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Wortmann, R., Ryan, L., Karas, B. et al. ECTO-NUCLEOSIDE TRIPHOSPHATE PYROPHOSPHOHYDROLASE ACTIVITY AND CALCIUM PYROPHOSPHATE DIHYDRATE CRYSTAL DEPOSITION DISEASE: 231. Pediatr Res 19, 782 (1985). https://doi.org/10.1203/00006450-198507000-00251
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DOI: https://doi.org/10.1203/00006450-198507000-00251