Choline Biosynthesis and Choline Requirement in the Rat as Affected by Coprophagy

Abstract

A study was made of the influence of several dietary and environmental factors on the dietary choline requirement of young rats. Under conditions of relatively low choline requirement which involve the absence of supplementary cystine and cholesterol and moderately low levels of fat and protein in the diet, prevention of coprophagy and possibly to some extent the inclusion of penicillin in the diet decreased the rat's requirement for choline. Coprophagy prevention completely protected from the high mortality related to kidney degeneration, and liver fat levels remained normal for the first 4 weeks postweaning. Methyl-labeled methionine tracer studies showed that transmethylation to form liver choline was high in rats 2 weeks post-weaning and declined to a lower level which reached a plateau at 6 to 8 weeks post-weaning. Choline deficiency lowered the early transmethylation rate, but the later plateau level was the same as for normal choline-fed animals. Coprophagy prevention raised the early transmethylation rate and choline biosynthesis in the choline-deficient animals so that it equaled the normal rate. It is proposed that prevention of coprophagy protects the young rat from choline deficiency by increasing choline biosynthesis. This effect is demonstrable only in the rat during the first 4 weeks post-weaning when the choline requirement is elevated and it is also observable only with dietary conditions that provide for a minimal choline requirement.