Immunocytochemical localization of catalase and heat-labile enoyl-CoA hydratase in the livers of normal and peroxisome proliferator-treated rats

The intracellular localization of catalase and the heat-labile enoyl-CoA hydratase (second enzyme of the peroxisomal fatty acid β-oxidation spiral) has been investigated using the protein A-gold immunocytochemical procedure in normal and peroxisome proliferator-treated rat livers. Peroxisome proliferation in rat liver was induced by the dietary administration of Wy-14,643 ([4-chloro-6-(2,3-xylidino)2-pyrimidinylthio]acetic acid). As expected, catalase was demonstrable exclusively in the matrix of all peroxisomes in hepatic parenchymal cells of normal and peroxisome proliferator-treated rats. The heat-labile enoyl-CoA hydratase, which was shown previously to be immunochemically identical with 80,000-molecular weight peroxisome proliferation-associated polypeptide, was also confined to the peroxisome matrix. The peroxisome nucleoids displayed no antigenic sites for any of these proteins. Both qualitative and quantitative evaluation of immunocytochemical labeling of catalase provide direct visual evidence for the decreased amount of this enzyme in proliferated peroxisomes when compared with normal peroxisomes. In contrast, the proliferated peroxisomes contained higher levels of heat-labile enoyl-CoA hydratase.