MICRODIALYSIS LIQUID-CHROMATOGRAPHIC STUDY ON COMPETITIVE-BINDING OF DRUGS TO PROTEIN

A new method to determine the interaction between drug and protein has been developed by utilizing the technique of microdialysis sampling w ith the ketoprofen and the human serum albumin (HSA) as the model of d rug and protein. Two kinds of binding sites of HSA to ketoprofen have been observed. The binding constants and number of binding sites obtai ned by the Scatchard equation are 0.799, 3.18,: x 10(6) mol(-1).L and 2.15, 2.01x10(5) mol(-1).L, respectively. The displacement binding of drugs to HSA has also been studied. The strong displacement of competi tive binding of ibuprofen with ketoprofen to HSA was observed, which m eans that :he primary binding site of HSA to ketoprofen and that to ib uprofen are the same. However, only a weaker displacement of warfarin for the association of ketoprofen with HSA was observed, which may sug gest that the primary binding site of HSA to ketoprofen is different f rom that to warfarin. Such a displacement effect for competitive bindi ng of drugs to HSA was explained by the displacement model in the liqu id-solid adsorption chromatography.