A comparative study of the carbohydrate content, protein, glycoprotein and ganglioside patterns of cell membranes isolated from Novikoff ascites hepatoma and normal liver

Abstract

Isolation of Novikoff ascites-hepatoma cell membranes in high yields from two different strains has been attained using an aqueous two-phase polymer system (dextran-polyethylene glycol). The degree of purity of the cell membrane fractions was determined by electron microscopy, estimation of marker enzymes (Na + + K +-ATPase, acid phosphatase, cytochrome c oxidase, NADH diaphorase) and chemical assays (RNA, DNA). It was found comparable to that obtained by other separation techniques. Gross analysis of sugars in the cell membranes of Novikoff hepatoma and normal rat liver showed minimal differences in sialic acid and hexosamine content. There were some differences in the carbohydrate composition of cell membranes of Novikoff hepatoma when compared to other ascites hepatomas. Paper chromatographic analyses of the bound-hexosamines in Novikoff hepatoma cell membranes as well as the agglutination tests of washed Novikoff ascites cells by specific lectins revealed the presence of N-acetylgalactosamine but failed to detect that of N-acetylglucosamine. Polyacrylamide gel electrophoresis of cell membrane proteins showed that the hepatoma was rich in low molecular weight proteins and poor in high molecular weight proteins and glycoproteins when compared to liver. Large amounts of hematosides were detected and a significant decrease in higher gangliosides homologues in hepatoma cell membranes were observed in contrast to a uniform distribution of the gangliosides in liver cell membranes. These results indicate that in spite of similar sugar contents in the cell membranes of normal rat liver and Novikoff ascites-hepatoma, there are important changes in their distribution in the glycoprotein and glycolipid constituents of the plasma membranes of the two cell types.