Displacement by uricosuric agents of sodium urate bound to human serum albumin

The displacement of sodium urate by uricosuric agents from binding sites on human serum albumin (HSA) and normal serum has been demonstrated under physiological conditions in vitro (pH 7.4, ionic strength 0.16) over he oncentration range 1–13 mg/100 ml. At 37°, 0.5 mM sodium salicylate reduced urate bound to 5 g/100 ml of HSA from 19.6 to 9.7 per cent. At 22.5°, 22.6 per cent urate was bound to 5 g/100 ml of HSA, and this was reduced to 12.3 per cent by 0.5 mM salicylate, to 9.2 per cent by 0.5 mM phenylbutazone, to 14.6 per cent by 0.2 mM diflumidone, and to 17.9 per cent by 0.2 mM sulfaethidole. At 22.5°, pooled normal human serum (4.8 g/100 ml of albumin) bound 23.5 per cent urate; with 0.5 mM salicylate present 12.6 per cent urate was bound.