In vitro calcium deposition by rachitic rat matrix vesicles: nucleoside triphosphate supported calcium deposition.
The present study was designed to test whether ATP at serum levels can support matrix vesicle-mediated Ca deposition while the final Ca x P ion product is maintained at or below serum or cartilage fluid levels. Rachitic rat epiphyseal cartilage matrix vesicles (40 micrograms protein/ml) in a simple calcifying solution (without exogenously added Pi) containing 50 mM Tris, pH 7.6 at 37 degrees C, 0.1 M NaCl, 1.35 mM CaCl2, 1 mM ATP, deposited about 500 nmol Ca/mg protein after 5 h. The amount of Ca deposited increased with increases in incubation time, concentrations of ATP, Ca2+, hydroxide, and matrix vesicle protein. UTP, GTP, and CTP were equally effective in supporting Ca deposition by matrix vesicles. ATP-alpha,beta-methylene and ATP-beta,gamma-methylene were inhibitory for ATP-dependent Ca deposition. Experiments with limiting amounts of ATP and Ca2+ available in the calcifying solution indicated that ATP concentration at serum levels, in the presence of Ca x P ion products at serum or cartilage fluid levels, can support matrix vesicle-mediated Ca deposition.
Hsu
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Department of Pathology and Oncology, University of Kansas Medical Center, Kansas City 66103.
D000255:Adenosine Triphosphate / Q000097:blood / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005109:Extracellular Matrix / Q000378:metabolism; D006132:Growth Plate / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010710:Phosphates / Q000378:metabolism; D051381:Rats; D012279:Rickets / Q000378:metabolism*; D013379:Substrate Specificity
D010710:Phosphates; D000255:Adenosine Triphosphate; D002118:Calcium