Reactive oxygen species and nitric oxide effect on the steroid hormone binding with serum albumin

Abstract

The interaction of a series of steroid hormones (DHEA, progesterone, testosterone, estradiol) with serum albumin immobilized on porous silica particles and the effect of reactive oxygen species and nitric oxide on this interaction were studied using a biochromatographic approach. The determination of enthalpy and entropy changes of this binding indicated that van der Waals interactions and hydrogen bonds predominated the hormone association with albumin. Reactive oxygen species (H(2)O(2) and OH*) increased the hormone binding affinity to albumin. On the other hand, this binding was decreased with the presence of NO*. This variation was due to conformational changes in the binding region explained by the oxidation of some residues such as free thiol and arginine. The thermodynamic analysis showed that free radical affects the van der Waals forces and/or a hydrogen bond of the hormone binding with albumin. These results explained the role of reactive oxygen species and nitric oxide in the hormone free fraction level in the blood.