PYROPHOSPHATE, PHOSPHATE ION INTERACTION - EFFECTS ON CALCIUM PYROPHOSPHATE AND CALCIUM HYDROXYAPATITE CRYSTAL-FORMATION IN AQUEOUS-SOLUTIONS

  • 1 January 1983
    • journal article
    • research article
    • Vol. 10  (5) , 769-777
Abstract
The relationship between ambient ionic conditions that favor pyrophosphate (PPi) vs. Pi biomineralization is important to understanding the pathogenesis of chondrocalcinosis. Aqueous solutions were studied at pH 7.4, 37.degree. C, [Na+] = 140 mM, [Mg2+] = 0.5 mM, [Ca2+] = 1.0 or 1.5 mM over a range of pyrophosphate and Pi concentrations to determine the effect of different ambient concentrations and ratios of Pi/PPi on pyrophosphate dihydrate (CPPD) and Ca hydroxyapatite (HA) crystal formation. The Pi/PPi ratio is an extremely important determinant of the crystal product formed. At low [Pi], CPPD crystal formation is partially inhibited by Pi; at higher [Pi], Ca pyrophosphate, Ca phosphate and Ca pyrophosphate-phosphate complexes amorphous to X-ray diffraction are formed; at still higher [Pi], HA crystal formation is partially inhibited by PPi. CPPD forms when the ratio [Pi]/[PPi] < 3 and HA forms when [Pi]/[PPi] > 100.