Induction by a-Mercapto-β-arylacrylic Acids of Low-molecular-weight Zinc-binding Protein in Rat Liver

Intraperitoneal injections of α-mercapto-β-(2-furyl)acrylic acid (MFA) induced incorporation of zinc into a low-molecular-weight metailoprotein fraction in ratqiver cytosol. Cytosol of control rats contained little or none of this material, α-Mercapto-β-(2-thienyl)acrylic acid induced less incorporation of zinc in this fraction than did MFA. Twenty-two hours after administration of ⁶⁵ZnSO₄ (50 μmol/kg) and MFA (200 μmol/kg), serum concentrations of both total and radioisotopic zinc were markedly elevated, compared to serum concentrations in rats administered only ⁶⁵ZNSO₄. Further, in liversof MFAtreated rats, radioisotopic zinc concentration was significantly greater in all cytosol zinc-containing proteins resolved by gel chromatogzaphy, but total zinc was elevated only in the metallothionein fraction and not in proteins of higher molecular weight. This appears to be the first example of induction of a metallothionein-like protein by a procedure not involving food restriction or administration of metal salts.