American Journal of Clinical Nutrition, Vol 19, 187-193, Copyright © 1966 by The American Society for Clinical Nutrition, Inc.

Folate and Vitamin B₁₂ Metabolism in Weanling Rats Given a Maize Diet

I. Folate and Vitamin B₁₂ Concentrations in Liver and Serum

¹ From the South African Institute for Medical Research, Johannesburg, South Africa

In weanling rats given a maize diet for six weeks, severe depletion of liver folate and vitamin B₁₂ concentrations occurred. The depletion of liver vitamin B₁₂ concentration was reflected by a fall in serum levels of vitamin B₁₂, but the serum Lactobacillus casei folate activity did not reflect the depleted folate stores. These observations are in accordance with the concept of a "pile-up" of L. casei-active material, in the form of N⁵-methyltetrahydrofolic acid, in vitamin B₁₂ deficiency.

When weanling rats fed maize were given supplements of pteroylglutamic acid (PGA) liver folate concentration was maintained, but vitamin B₁₂ deficiency was not prevented. Supplementation with vitamin B₁₂ prevented depletion of both vitamin B₁₂ and folate in the liver, but the serum L. casei folate activity decreased markedly.

Refeeding a stock diet to rats previously subsisting on a maize diet resulted in a rapid increase in the liver concentration of folate and vitamin B₁₂. Supplementation with PGA and vitamin B₁₂ did not significantly accelerate the repletion of the liver stores in refed rats.