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.