Orcein positive hepatocellular material in long-standing biliary diseases. I. Histochemical characteristics

Orcein positive material, which accumulates in liver cells in long-standing biliary diseases, was studied histochemically in 5 patients with primary biliary cirrhosis. The material was highly basophilic after previous oxidation of tissue sections and could be demonstrated by orcein at pH 2, alcian blue at pH 0.2, and toluidine blue at pH 2.5. The comparative experiments suggested that sulphonic acid residues in orcein positive material after the oxidation were responsible for the staining reactions. In addition, the staining characteristics indicated the protein nature of the material. The staining reactions suggested that orcein positive material is associated with copper in liver cells and indicated the presence of a copper-protein complex. In contrast to orcein and alcian blue reactions, the oxidation of tissue sections abolished the positive histochemical reaction for copper. This was considered to indicate a dissociation of the copper-protein complex and an oxidation of the liberated sulphydryl groups to sulphonic acid residues, which are probably responsible for the basophilic staining reactions.