INFLUENCE OF IONIC-STRENGTH ON CRYSTAL ADSORPTION AND INHIBITORY ACTIVITY OF MACROMOLECULES

We investigated the influence of ionic strength on both the binding ab ility of macromolecules onto calcium oxalate crystals and the inhibito ry activity of macromolecules related to calcium oxalate crystal growt h and aggregation in vitro. The amount of heparin sodium salt adsorbed onto calcium oxalate crystals was studied in both a seed and a non-se ed crystal system at various ionic strengths with the aid of radiolabe lled heparin. In both adsorption models, adsorption of heparin was gre ater in the buffered solutions of lower ionic strength, and significan tly so in the range of physiological ionic strength. The inhibitory ac tivity of heparin in the non-seed crystal system, which was determined using a Coulter Multisizer, increased as the adsorbed dose increased. The naturally existing urinary macromolecules showed a similar change in their inhibitory activity on calcium oxalate crystal growth and/or aggregation in accordance with changes in ionic strength. These resul ts indicate that macromolecular inhibitory activity seems to be enhanc ed in urine of lower ionic strength as a result of an increased adsorp tion of macromolecules on the surface of calcium oxalate crystals.