Lack of protein-mediated alpha-tocopherol transfer between membranes in the cytoplasm of ascites hepatomas.

Transfer-stimulating activity for alpha-tocopherol and the concentration of alpha-tocopherol and peroxidized lipids in rat ascites hepatoma cells were compared with those from normal and regenerating liver. The ability of supernatants from ascites hepatomas (AH-13, AH-60C, AH-109A) to enhance the transfer of alpha-tocopherol was much lower than that from normal livers. The alpha-tocopherol per mg protein of supernatant from ascites hepatomas was lower than that from normal liver. Regenerating liver showed almost the same values as normal liver in activity to stimulate the transfer of alpha-tocopherol and alpha-tocopherol content of the supernatant. By gel filtration, about 60% of alpha-tocopherol in the supernatant of normal liver was detected in the fractions containing the 30 K protein, which stimulates transfer of alpha-tocopherol between membranes, whereas no significant amount of alpha-tocopherol was detected in 30 K protein fractions of AH-60C supernatant. Little stimulating activity for alpha-tocopherol transfer was detected in AH-60C, AH-109A and AH-13. All ascites hepatomas tested contained less arachidonic acid and docosahexaenoic acid than normal and regenerating liver. An absorption peak with maximum intensity at 233 nm, which is due to conjugated dienes, was observed in UV-absorption spectra of ascites hepatoma total lipids, indicating that peroxidized lipids accumulate in these cells. With normal and regenerating liver, no significant peak due to conjugated dienes was detected.