In vitro inhibition of the soluble glutathione S-transferases from rat liver by heavy metals.

The in vitro inhibition of the soluble glutathione S-transferases (GST) from rat liver by heavy metals is studied. Added at 200 mumol/l to the incubation mixture, no inhibition was found for CsCl, RbCl, BaCl2, MnCl2, NiCl2 . 6H2O, PbCl2, SnCl2 . 2H2O, SrCl2 . 6H2O, AlCl3, and ZrCl4, but HgCl2, CuCl2 . 2H2O, and CdCl2, and H2O inhibited the GST activity for respectively 82, 50 and 37%. A method is presented for the separation of the seven soluble GST isoenzymes in one chromatographic run. Each of them is inactivated by mercury, copper (II), and cadmium, albeit to different degrees. The inhibition capacity of cadmium does not seem to be dependent on both the substrate and the enzyme concentration. Mercury and copper (II) interact directly with GST, although they do with glutathione as well. Cysteamine and cysteine reverse the heavy metal inhibition of GST. Sulfhydryl groups are thus important for the function of GST.