Folic acid metabolism in normal, folate deficient and alcoholic man

Folate metabolism was studied in normal, folate-deficient and alcoholic man by tracer measurements of plasma clearance, urinary excretion, tissue storage and release of folate using both [3H]pteroylglutamic acid (3H-PteGlu) and 14C-methyl-H4PteGlu. Alcohol ingestion did not adversely affect tissue uptake of folates. Whether in normal or folate deficient subjects, the relative clearance rates of 3H-PteGlu and 14C-methyl-H4PteGlu were maintained in the face of alcohol ingestion and there was no evidence of increased urinary loss of intact vitamin or labelled breakdown products. As measured by the flushing technique, the rate of storage or tissue binding of 3H-PteGlu was not influenced by folate deficiency, folate store depletion or alcohol ingestion. However, alcohol may retard the release of methyl-H4PteGlu from tissue stores to plasma. A significantly greater recovery of 14C-methyl-H4PteGly with flush was observed in those normal subjects who ingested alcohol for 6 d. A partial block in the rate of release of tissue folate stores would be a possible mechanism behind the rapid depression in serum methyl-H4PteGlu levels and early induction of megaloblastic erythropoiesis which has been observed following acute alcohol ingestion.