Abnormal haem biosynthesis in chronic alcoholics.

The activities of six of the enzymes of haem biosynthesis have been examined in eleven chronic alcoholics admitted to hospital for alcohol withdrawal. The mitochondrial enzymes delta-aminolaevulinic acid (ALA) synthase, coproporphyrinogen oxidase and ferrochelatase were monitored in peripheral leucocytes and the cytosolic enzymes ALA dehydratase, uroporphyrinogen-1-synthase and uroporphyrinogen decarboxylase in peripheral erythrocytes. Compared with control subjects the activity of the initial and rate controlling enzyme of the pathway, ALA synthase, was increased (P less than 0.01) and the activities of ALA dehydratase and uroporphyrinogen decarboxylase depressed (P less than 0.01, P less than 0.02 respectively) on the day after admission but all returned to normal by the tenth to twentieth days after alcohol withdrawal. This stimulation of ALA synthase and inhibition of uroporphyrinogen decarboxylase explains the mechanism by which chronic alcohol ingestion may precipitate cutaneous hepatic porphyria. Two of the alcoholics were anaemic without evidence of haematinic deficiency and this was associated with depressed ferrochelatase activity and iron and porphyrin accumulation. The anaemia and related biochemical abnormalities in these two subjects were all corrected with alcohol withdrawal. It is proposed that inhibition of ferrochelatase activity is the biochemical basis of alcohol related sideroblastic anaemia.