The Influence of Pteroylglutamic Acid and Vitamin B12 on the Metabolism of Pyridine-fed Rats

Abstract

Rats were given a basal purified diet containing 15% casein. The addition to this diet of 1% pyridine suppressed growth, creatine excretion, and liver choline oxidase activity. The addition of vitamin B₁₂ to the pyridine diet improved the growth of the rats, and the addition of either vitamin B₁₂ or pteroylglutamic acid resulted in increased liver choline oxidase activity. The addition of a combination of pteroylglutamic acid and vitamin B₁₂ to the diet of rats receiving 1% pyridine resulted in a greatly increased excretion of creatine; rats receiving this diet grew at a normal rate the first 20 experimental days but at a reduced rate thereafter. Three of the 8 rats receiving the pyridine diet supplemented with the combination of pteroyglutamic acid and vitamin B₁₂ died between the 30th and 35th experimental days; on autopsy the livers of all rats in this group were yellow and infiltrated with fat. There was no evidence of fatty infiltration in the livers of rats receiving any of the other diets. It is suggested that methylating reactions are stimulated in the presence of pteroylglutamic acid and vitamin B₁₂, resulting in an increased methylation of the pyridine. The excretion of this methylated pyridine would result in a deficiency of methyl, with the consequent production of fatty livers.