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

Abstract

Amount of Ca2+ adsorbed by calcium oxalate (CaOx) in the presence of sodium chondroitin6-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 surfac e owing mainly to large protruding loops of adosrbed Chs2-. Oxalate anion (0x2-) 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) becaus e conformational change of the adsorbed Chs2- strongly affects the adsorption amount of 0x2-. Na2Chs showed a dispersing effect on the precipitate of CaOx through its adsorption (Figs.6and 7). The role of Na2Chs in inhibition of formation of urinary stones of CaOx was discussed on the basis of its dispersing/adsorption effect.