INFLUENCE OF NONSTEROIDAL ANTIINFLAMMATORY DRUGS ON THE BINDING-KINETICS OF DANSYLSARCOSINE TO HUMAN SERUM-ALBUMIN - STEREOSELECTIVITY, STERIC AND INDUCTIVE EFFECTS

The effect of a series of non-steroidal anti-inflammatory drugs (NSAID s) on the binding kinetics of dansylsarcosine (CAS 72517-44-3, DS), a marker ligand for the benzodiazepine binding site, and human serum alb umin (HSA) was studied using the stopped-now method. Both native (7 % glycated) and 25 % glycated HSA were used. The binding parameters were determined on the basis of the consecutive model. The DS association rate constant (k(2)) was 649 +/- 84 s(-1) and 375 +/- 13 s(-1) for 7 % and 25 % glycated HSA, respectively. These values were substantially influenced by addition of NSAIDs (molar ratio HSA:NSAID = 2:1), depend ing on the structure of NSAIDs. The calculated DS dissociation rate co nstant (k(-2)) was approximately 20 s(-1) this value did not show mark ed dependence on the degree of glycation or on the presence of NSAIDs at the concentration used. The values were similar to estimates of k(d ) (the displacement rate constant of DS) with the exception of diclofe nac (CAS 15307-86-5) where k(d) was significantly lower, reaching 4.8 +/- 0.4 s(-1) and 4.8 +/- 0.6 s(-1) vs. k(-2) parameters of 14 +/- 2.8 s(-1) and 15 +/- 3.7 s(-1) for 7 % and 25 % glycated HSA, respectivel y. A comparison of the enantiomers R- and S-ibuprofen (CAS 15687-27-1) and the regioisomers fenbufen (CAS 36330-85-5) and ketoprofen (CAS 22 071-15-4) showed slight or no stereoselectivity of effects on the DS b inding kinetics. However, the binding was influenced by bulk and natur e of substituents at the aryl rest of propionic acid. The results obta ined for mefenamic acid (CAS 61-68-7) suggest that this NSAID binds to a site of human serum albumin other than site II, Increased concentra tions of glycoalbumin, as observd in diabetic patients, are not presum ed to have inhibitory effects additional to that of NSAIDs which inter act differentially with drugs at site II of HSA.