The effect of nitrous oxide inactivation of vitamin B12 on rat hepatic folate. Implications for the methylfolate-trap hypothesis

Abstract

Rats exposed to N2O show a decrease in liver folate to about 25% of the initial value after 10 days. There is a transient increase in the amount of 5-methyltetrahydropteroylpolyglutamate in the first 24 h, but thereafter the content decreases. The level of 5-methyltetrahydropteroylmonoglutamate declines without any transitory increase. The transient accumulation of 5-methyltetrahydropteroylpolyglutamate is due to failure of methionine synthetase. Thereafter the decrease in the amount of methylfolate makes it improbable that trapping of methylfolate is the explanation of failure of folate metabolism in vitamin B12 deficiency.