Effects of ligands on gold inhibition of selenium glutathione peroxidase

Gold inhibits selenium-dependent glutathione peroxidase (GSH Px) in vitro. Chrysotherapy has been used for over five decades without complete understanding of its pharmacodynamics. This study shows that gold is potentially an inhibitor of GSH Px in vivo. Reported are conditions for assay of GSH-Px activity showing that the inhibition by gold species can be reversed. The study demonstrates the high affinity of gold for the selenohydryl-active site of GSH Px relative to the affinities of other physiological ligands; GSH Px was inhibited to a greater extent by a small molecular-weight fraction isolated from kidneys of gold-treated rats than by the fraction isolated from kidneys of rats not treated with gold. The data provide a new perspective on the action of gold-containing drugs in vivo.