Vitamin B12 deprivation in the rat: effects on folate metabolism with emphasis on the nervous system

Rats were subjected to deprivation of vitamin B12 in order to induce neuropathy and to study effect on folate metabolism. Plasma vitamin B12 concentrations were maintained at about 100 pg/ml for 5 months. Neurological testing failed to reveal signs of neuropathy. Vitamin B12 deprivation induced high plasma folate levels but had no effects on the levels of total folate in the liver or the nervous system, probably because of an adequate methionine supply. If the rats were starved, a smaller proportion of 5-methyltetrahydrofolate was found both in liver and brain of the vitamin-B12-deprived animals. The folate concentration in the cerebrospinal fluid was lower than in the plasma but the values were correlated. There was a striking similarity between the liver and the brain in the way of handling 3H-folic acid and 14C-methyltetrahydrofolic acid. However, both substances showed a higher specific activity in the brain than in the liver, indicating a more dynamic state of brain folate.