1. Plasma membranes were isolated from normal liver,
Morris hepatoma 7288C and regenerating liver, 6, 15, 24, and 48 hr after partial
hepatectomy. 2. The
cholesterol/
phospholipid ratio was lower in regenerating liver 6 hr after partial
hepatectomy (0.51) compared to the
sham control (0.68), returning to normal after 15 hr. This was accompanied by a small increase in
palmitic acid (16:0). There were no other changes in the
lipid composition in regenerating hepatocytes in the first 48 hr after partial
hepatectomy. 3. Analysis of
lipid composition showed a higher
cholesterol/
phospholipid ratio in the
hepatoma plasma membrane compared to normal liver accompanied by an increase in saturation of the fatty acyl groups of the
phospholipids. There were also significant changes in the
phospholipid classes. 4. There was no change in the two-dimensional electrophoretic profile of
membrane proteins in the early stages of liver regeneration, however
hepatoma membranes showed significant differences in
protein profile. 5. These changes in the
lipid composition of the
hepatoma plasma membrane would have the effect of decreasing the average fluidity of the membrane and together with the changes in
protein composition may be significant in the altered growth of the
hepatoma. Changes in the
lipid composition of the hepatocyte plasma membrane early in liver regeneration may reflect the onset of renewed cell division.