Abstract
One in vitro model of the chondro-osseous dysplasia (COD) seen in adenosine deaminase deficiency is characterized by depletion of chondrocyte ATP. If normal bone mineralization is an energy dependant process, low growth plate ATP concentration could be a partial basis for COD. Since cartilage matrix vesicles (MV) are involved in mineralization of growth cartilage and MV possess an ensemble of membrane bound purine nucleotide-processing enzymes including ATP pyrophosphohydrolase, 5′nucleotidase and alkaline phosphatase, we investigated whether ATP was required for MV mineralization.
MV were prepared by ultracentrifugation of collagenase-digested adult porcine hyaline articular cartilage. Mineralization experiments were conducted in inorganic phosphate (Pi)-free media containing 2.2mM 45Ca at ph 7.6 and 37° C. Additions of ATP, AMP, Pi, αB-methylene ATP were made in various experiments. Mineralization was expressed as 45Ca uptake in MV separated by 0.45 micron membrane filtration. Mineralization occured by 6 hours in the presence of 0.5-1.5 mM ATP or βγmethylene ATP but not with stoichiometric added Pi alone. Mineralization was inhibited by 5 mM ATP. AMP alone only poorly supported mineralization, and no mineralization was observed with αβ-methylene ATP.
ATP requirement for MV mineralization indicates the potential importance of this simple model in studing the mechanisms of defective bone-formation in COD.
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Rachow, J., Chowdhurry, M. & Wortmann, R. 175 ATP-DEPENDENT MINERALIZATION OF HYALINE ARTICULAR CARTILAGE MATRIX VESICLES. Pediatr Res 24, 140 (1988). https://doi.org/10.1203/00006450-198807000-00199
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DOI: https://doi.org/10.1203/00006450-198807000-00199