Immunohistochemical demonstration of the cytoplasmic copper‐associated protein in the liver in primary biliary cirrhosis: its identification as metallothionein

Abstract

— Metallothionein was isolated from the liver of rats pretreated with cadmium. Monospecific anti-metallothionein antibodies were produced in rabbits. Twenty-six primary biliary cirrhosis (PBC) liver samples and three control liver samples were stained for metallothionein by an indirect immunoperoxidase technique. Nineteen of the PBC samples and the control samples were also stained for copper by Timm's silver sulphide method. In all PBC samples the copper concentration was determined. In addition, the zinc, cadmium, and mercury concentrations were measured in some samples. Eighteen of the PBC samples stained for metallothionein showed marked diffuse cytoplasmic and nuclear staining of a varying number of periportal hepatocytes. In none of them was granular staining detected. None of the control samples showed staining. Fourteen of the PBC samples stained for copper showed diffuse cytoplasmic and granular staining of the periportal hepatocytes. In none of them was nuclear staining detected. None of the control samples showed staining. No elevated zinc, cadmium, or mercury concentrations were found but the copper concentration was increased in 21 of the 26 PBC samples. The number of cells staining for copper and metallothionein was assessed semiquantitatively. Significant correlations were found between the grade of metallothionein staining and the liver copper concentration; the grade of Timm's staining and the liver copper concentration; and the grades of metallothionein staining and Timm's staining. The data suggest that the accumulation of copper induces synthesis of cytoplasmic and nuclear metallothionein, and that the increased amount of cytoplasmic copper is bound to a similarly increased amount of metallothionein.