RESUMEN
The effect of a series of non-steroidal anti-inflammatory drugs (NSAIDs) on the binding kinetics of dansylsarcosine (CAS 72517-44-3, DS), a marker ligand for the benzodiazepine binding site, and human serum albumin (HSA) was studied using the stopped-flow 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 (k2) 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), depending on the structure of NSAIDs. The calculated DS dissociation rate constant (k-2) was approximately 20 s-1. this value did not show marked dependence on the degree of glycation or on the presence of NSAIDs at the concentration used. The values were similar to estimates of kd (the displacement rate constant of DS) with the exception of diclofenac (CAS 15307-86-5) where kd 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, respectively. A comparison of the enantiomers R- and S-ibuprofen (CAS 15687-27-1) and the regioisomers fenbufen (CAS 36330-85-5) and ketoprofen (CAS 22071-15-4) showed slight or no stereoslectivity of effects on the DS binding kinetics. However, the binding was influenced by bulk and nature of substituents at the aryl rest of propionic acid. The results obtained for mefenamic acid (CAS 61-68-7) suggest that this NSAID binds to a site of human serum albumin other than site II. Increased concentrations of glycoalbumin, as observed in diabetic patients, are not presumed to have inhibitory effects additional to that of NSAIDs which interact differentially with drugs at site II of HSA.