Relationship between SH group reactivity and concentration of bovine serum albumin and rat plasma

This study revealed that SH group reactivity (R) and concentration (C) of bovine serum albumin (BSA) and rat plasma are proportional in the sulphydryl-disulfide (SH-SS) exchange reaction with 5-5' dithiobis (2nitrobenzoic acid) (DTNB). The existence of the R/C proportionality suggests the use of Kr ratio and C as parameters for characterizing the biological properties of plasma SH groups. Moreover it was found that the electrophilic agents, diethylmaleate (DEM) and ethacrynic acid (ETHAC) that react with SH groups, determine an in vitro decrease in plasma SH group concentration and a Kr increase. The Kr increase seemed to be independent of SH group blocking as results obtained with sodium dodecyl sulfate (SDS) and SDS plus DEM indicated. The Kr biological significance might be related to a conformational change of albumin. In vivo treatment with 0.6 and 1.2 ml/kg of DEM confirmed the plasmatic linear relationship between R and C and showed a Kr increase in accordance with in vitro results. In carrageenan paw edema, decreased SH group plasma levels and an increased Kr were obtained.