POLYMERIC SORBENTS FOR BILE-ACIDS .4. TREATMENT OF CHOLESTYRAMINE AS A DONNAN SYSTEM

Isotherms have been determined for the in vitro sorption of cholate and glycocholate bile salt anions by cholestyramine, under various conditions of buffer and temperature. It is shown that a change in the counter-ion of the resin, from chloride to iodide, generally results in decreased sorption. Arguments based on Donnan concepts are developed to show that the binding involves ion exchange that is accompanied by the aggregation of bile salt anions within the resin phase. The derived binding constant is found to be concentration dependent, suggesting the importance of such cooperative effects.