EFFECT OF SODIUM CHONDROITIN-6-SULFATE ON THE ADSORPTION OF CALCIUM AND OXALATE IONS BY CALCIUM-OXALATE MONOHYDRATE AND ON THE PRECIPITATE FORMATION OF CALCIUM-OXALATE

Amount of Ca2+ adsorbed by calcium oxalate (CaOx) in the presence of sodium chondroitin-6-sulfate (Na2Chs) is composed of 2 components ; the first is that directly adsorbed by the surface of CaOx and the second that captured by the adsorbed chondroitin-6-sulfate ion (Chs2-) as its counter ion. It was found that the former depends on the concentration of Ca2+ free from both Chs2- and CaOx in a mother solution (Fig.3). The binding ratio of Ca2+ to ChS2- was almost the same between that in the solution and that on the surface owing mainly to large protruding loops of adosrbed Chs2. Oxalate anion (Ox2-) competed for the adsorption sites on CaOx with Chs2- (Fig. 4). Sum of the adsorption amounts of ChS2- and OX2- behaved complicatedly with the adsorption amount of Chs2-(Fig. 5) because conformational change of the adsorbed Chs2- strongly affects the adsorption amount Of OX2-. Na2Chs showed a dispersing effect on the precipitate of CaOx through its adsorption (Figs. 6 and 7). The role of Na2Chs in inhibition of formation of urinary stones of CaOx was discussed on the basis of its dispersing/adsorption effect.