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Methylation of Nicotinamide in Vitamin B₁₂- and Vitamin B₆-Deficient Rats

Department of Biochemistry, The Johns Hopkins University, School of Hygiene and Public Health, Baltimore, Maryland

The effect of vitamin B₁₂ deficiency on methylation, as indicated by the urinary excretion of methylnicotinamide following the administration of nicotinamide, was studied. It was found in male and female rats that dietary deprivation of this vitamin brought about a decrease in methylation. This effect is not due to nonphysiologic causes since pair-fed animals from both deficient and treated groups, as well as female rats in these two groups, exhibited a significant difference in excretion. Furthermore, vitamin B₆ deficiency does not bring about such a difference. However, if vitamin B₆ deficiency were prolonged, vitamin B₁₂ serum level of these vitamin B₆-deprived animals was reduced. Only then did a decrease in methylation occur. From these studies, it was concluded that vitamin B₁₂ deficiency by dietary deprivation or by poor absorption of this vitamin decreases the urinary excretion of MNA.

Manuscript received 4 November 1961.