Studies on rat liver plasma membrane. Altered protein and phospholipid metabolism after injection of d-galactosamine

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Abstract
The metabolism of protein and phospholipid in rat liver plasma membranes isolated by the method of Neville was investigated 3 and 6 h after the injection of D-galactosamine in vivo. During this time, all the biochemical and morphological alterations associated with hepatitis developed. After injection of D-galactosamine the concentration of sphingomyelin in the plasma membrane decreased to < 60% of the control values. Activity of 5''-nucleotidase (EC 3.1.3.5), which was purified as a sphingomyelin-protein complex, decreased in the total homogenate as well as in the plasma-membrane fraction of livers of rats treated with galactosamine, to about 60% of the control values. Protein synthesis, as measured by the incorporation of [14C]leucine into plasma membranes, was decreased to 45% of that of the controls. Only small differences were observed in the amino acid composition of the plasma membrane after D-galactosamine treatment. The protein composition of the plasma membranes was determined by sodium dodecyl sulfate/polyacrylamide-gel electrophoresis. Results showed a change from low to high MW proteins after the injection of galactosamine. These results demonstrate different metabolic processes of the plasma membrane altered during induction of galactosamine hepatitis.