Phospholipid content of mitochondrial and microsomal membranes from Morris hepatomas of varying growth rates.

Mitochondria and microsomal membranes were prepared from normal, fetal, and regenerating rat liver and from seven Morris hepatomas of varying growth rates and analyzed for percentage of phospholipid composition and phospholipid con tent per mg protein. The Morris hepatomas studied included the7777,5132tc,7800,7794A,7787,9633,and 96i8A. Cardiolipin is localized in mitochondria in all tissues studied. The sphingomyelin percentage and content are increased in mitochondria of fetal rat liver and more rapidly growing hepa tomas, 7777, 5123tc, and 7794A but are similar to those of normal liver in hepatomas with slower growth rates. The ratio of the percentage of phosphatidylethanolamine to that of phos phatidylcholine in mitochondria and microsomes is not sub stantially altered in most of the seven hepatomas and in the rapid growth controls. Our studies do not support the conceà ̃t of equalization of membrane phospholipid composition in hep atomas with regard to the subcellular localization of cardiolipin and the ratios of percentage of phosphatidylethanolamine to that of phosphatidylcholine. However, our results confirm the increased percentage of sphingomyelin in the membranes of hepatomas with very rapid growth rates. Substantial changes in the membrane phospholipid content per mg of protein are present in the seven Morris hepatomas. The mitochondrial phospholipid content per mg of protein is substantially increased in nearly all of the hepatomas and in fetal liver but appears to be normal in regenerating rat liver. Microsomal phospholipid per mg of protein is considerably decreased in nearly all of the hepatomas and in the rapid growth controls. Changes in membrane phospholipid content per mg of protein appear to be of a greater quantitative signif icance in these Morris hepatomas than are alterations in the percentage of phospholipid composition of the respective membrane fractions.