1. Triacylglycerol in erythrocytes from normal human subjects was estimated to average 2.7 ± 0.7 nmol/1010 cells, equivalent to 0.07% of total lipids or 0.3% of neutral lipids.
2. The specific activity of triacylglycerol labelling attained by incubating intact erythrocytes with [3H]oleic acid was 10 nmol/μmol, a value 20-fold higher than that of the highest labelled phospholipid, sphingomyelin; as isolated by ultracentrifugation over a density gradient, the youngest erythrocytes exhibited a labelling rate 10-fold higher than that of older cells.
3. The triacylglycerol content was not modified in erythrocytes from chronic alcoholics, whereas the mean rate of triacylglycerol labelling was 31% (P <0.05) higher than that of control subjects, and did not normalize 4 weeks after alcohol withdrawal.
4. These results indicate that triacylglycerol, although a quantitatively minor component, is one of the most active metabolites in the lipid matrix of the human erythrocyte membrane and appears to be implicated in the membrane response to antagonistic agents.