The fatty acid composition of mitochondria, microsomes and myelin from neonatal chick brain. Susceptibility to short and chronic treatment with ethanol

Physical properties, lipid composition and enzyme activities of hepatic subcellular membranes from chick embryo after ethanol treatment

Exposure of chick embryos to ethanol resulted in significant alterations to the lipid composition of various different hepatic subcellular membranes. A marked decrease in cholesterol levels and an increase in the phospholipid content of microsomes and mitochondria was observed. Ethanol also affected the fatty acid profiles, mainly by decreasing the percentage of oleic acid in phosphatidylcholine and phosphatidylethanolamine in the mitochondria and phosphatidylethanolamine in the microsomes. In spite of these changes ethanol only induced alterations in the fluidity of the mitochondrial membranes, which showed a more rigid core, in contrast to the phospholipid-head region, which was not affected. In accordance with the changes observed in the physical state of the membrane, the enzymes involved in the microsomal electron-transport systems were not modified by ethanol, while cytochrome oxidase activity decreased by 50% compared to the activity in the mitochondria from control chick embryos. These findings establish that during the chick-embryo developmental period the mitochondria are more sensitive to ethanol than are the microsomes.

Ethanol and lipid metabolism. Differential effects on liver and brain microsomes

We have determined the effect of prolonged ethanol treatment on several enzyme activities related to lipid metabolism in chick-brain and liver microsomes. Ethanol increased microsome cholesterol levels in both organs. The treatment caused a marked increase in the hepatic HMG-CoA reductase and ACAT activities while in the brain a clear decrease was found in these enzyme activities. At the same time the activity of reacylation of phospholipids, was clearly modified in both brain and liver. Thus, while in the liver the turnover of acyl moieties of phosphatidylethanolamine, sphingomyelin and phosphatidylinositol was enhanced by ethanol consumption, in the brain only the reacylation of phosphatidylserine increased to any significant extent. These results indicate that ethanol exerts a differential action in brain and liver, namely cholesterol synthesis and esterification decreased in brain and increased in chick liver. Ethanol also induces faster phospholipid metabolism in both brain and liver microsomes.

Concentration differences in isoforms of transferrin in blood from alcoholics during abuse and abstinence

At least five different forms of iron-saturated transferrin (Tf) from blood plasma can be separated by isoelectric focusing. These transferrin forms differ in the carbohydrate parts, especially the amount of sialic acid. The increased relative concentration of the form with isoelectric point 5.7 (Tf5.7) has been shown to be a good indicator for liver effects caused by alcohol abuse. However, in alcoholics during abstinence the newly formed transferrin has a higher sialic acid content than most of the transferrin already present in the blood. This indicates that the elevated concentration of Tf5.7 with a low sialic acid content, found in alcoholics is not due to a defect at sialylation, but most probably caused by an impaired uptake of sialic acid-deficient transferrin by the hepatocytes due to membrane dysfunction.