1. The concentrations of the acid soluble and insoluble coenzyme A (CoA) esters were measured in samples of liver obtained at autopsy from Reye's syndrome and control subjects because the long chain fatty CoA compounds which make up the bulk of the acid insoluble CoA esters are known to inhibit a number of mitochondrially located enzymes, several of which may be affected in Reye's syndrome.
2. Concentrations of the acid insoluble esters varied widely in both control and Reye's liver samples. The difference between the mean values was not statistically significant (1·06 ± sem 0·33 nmol/g wet weight in Reye's samples vs 0·88 ± 0·21 in control samples).
3. Concentrations of the acid soluble CoA esters, which include the short chain fatty CoA compounds, were higher in Reye's liver samples than in samples from controls. The mean value for Reye's samples was 104·8 ± sem 29·4 nmol/g of liver compared with 26·4 ± 10·1 nmol/g for control samples (P < 0·05).
4. Studies with rats designed to assess postmortem change indicate that the liver concentration of the acid insoluble CoA compounds does not change during a 4 h period at 4°C. This finding suggests that the observations made in Reye's liver was probably due to a premorbid abnormality.
5. These findings implicate a block in the β-oxidation of fatty acids and could account for the reported relative increase in the concentrations of the short to medium chain fatty acids in the plasma of Reye's syndrome patients.