[Interaction of suprofen and serum albumin]

The serum albumin-interaction of suprofen (SPF), a novel anti-inflammatory drug, was compared with those of indomethacin (IM) and ketoprofen (KTP). The binding constants of these drugs were determined with difference absorption spectra based on the binding to bovine serum albumin (BSA). The constants for SPF and IM were nearly equal, and the value for KTP was smaller than those of the other drugs. The magnitude of the inhibitory effect on heat denaturation of BSA reflected the difference in these binding constants. In the presence of these drugs, the tryptophan fluorescence in BSA was quenched (IM, SPF and KTP, in this order). The metachromagy based on the binding of an azodye, HABA, to BSA was potentiated by IM or SPF. Phenylbutazone suppressed the absorption of the metachromagy. SPF displaced only the binding of the fluorescent Site II probe, dansylproline, to human serum albumin (HSA), and both the bindings of dansylproline and dansylamide (Site I probe) to HSA were inhibited by KTP or IM. KTP released bilirubin from BSA and HSA, but SPF and IM did not show any effects on the bilirubin-serum albumin binding. These results all support that there is considerable interaction between SPF and serum albumin and that the mode of the interaction differs from those of KTP and phenylbutazone.