Analysis of the progesterone displacement of its human serum albumin binding site by β-estradiol using biochromatographic approaches: effect of two salt modifiers

The mechanisms of (i) the binding of two sex-hormones (i.e. progesterone and β-estradiol) to human serum albumin (HSA) and (ii) the progesterone displacement of its HSA binding cavity by β-estradiol were studied by biochromatography using three different methods. In the first time, zonal elution method was used to prove the direct competition effect between the two sex-hormone. In the second time, the competition effect between β-estradiol and progesterone to bound on the same HSA site was analysed by the competitive bi-Langmuir approach. Finally, the thermodynamic data of these two binding processes were studied. The Gibbs free energy value (ΔG̃°) of the displacement equilibrium was negative demonstrating that β-estradiol displaced progesterone of its HSA binding cavity. Moreover, the effect of two chloride modifiers (i.e. Na+, Mg2+) on these two binding processes were analysed. Results showed that in the salt biological concentration ranges, the Mg2+ cation enhanced strongly the bioavailable progesterone, whereas the Na+ cation interacted slowly on the progesterone displacement of its HSA binding site by β-estradiol. This study showed that it must be useful to carry out more in vivo test on the magnesium supplementation effect for women who suffer from estrogen dominance syndrome.