Subcellular particles in tumors—III: Peroxisomal enzymes in hepatoma HC and Morris hepatomas 7794A, 7794B, 5123A and 7316A

Abstract

(1) The activities of catalase, d-amino acid oxidase and urate oxidase have been measured in the hepatoma HC and four Morris hepatomas and compared with those found in the rat liver. (2) Catalase shows the phenomenon of latency in homogenates of the hepatomas 7316A, 7794B, 5123A and HC; its activity is very increased by the presence of Triton X- 100 in the incubation medium. The detergent has no effect on catalase of the hepatoma 7794A. (3) The intracellular distribution of these enzymes has been investigated according to the centrifugation scheme of de Duve and coworkers [16]. In the hepatomas 7316A, 7794B, 5123A and HC, the enzymes are mainly recovered in the mitochondrial fractions and exhibit a peak of specific activity in the light one. In the hepatoma 7794A, catalase and d-amino acid oxidase are chiefly present in the soluble fraction. (4) The total mitochondrial fractions of the hepatomas 7316A, 7794B, 5123A and HC have been analysed by isopycnic centrifugation in a sucrose gradient and in gradients made of glycogen dissolved in aqueous sucrose of different concentrations. Catalase, d-amino acid oxidase and urate oxidase of the hepatomas 7316A, 7794B and 5123A exhibit similar distribution patterns. The densities of the particles bearing the enzymes linearly increase as a function of the sucrose concentration of the medium. A similar phenomenon is observed for catalase of hepatoma HC. (5) These results are discussed with respect to the presence of peroxisomes in the hepatomas and to their properties.