Dietary factors related to liver xanthine oxidase.

In a previous study (1) it was shown that dogs maintained on a purified diet developed a defect in acetaldehyde metabolism. Of the five known enzyme systems that could theoretically be involved in acetaldehyde metabolism in viva (aldolase, mutase, carboxylase, aldehyde ox&se, and xanthine oxidase), the xanthine and aldehyde oxidases seemed most likely to be dependent upon a dietary factor not already incorporated in the purified rations used. Our attention was therefore directed to a study of the relationship between liver xanthine oxidase in rats and the dietary factors supplied to the animals. In this way it was observed that some unidentified factor had to be supplied in the diet in order to obtain normal levels of xanthine oxidase in the liver (2). Previous studies have implicated both riboflavin (3) and protein (4) as essential dietary factors required by the rat for the establishment of normal xanthine oxidase levels in the liver. Inanition has also been shown to decrease liver xanthine oxidase in the rat (5). Keith et al. (6) reported that the incorporation of less than 1 mg. per cent of folic acid in a purified diet decreased the xanthine oxidase activity of chick livers, but as far as rat liver xanthine oxidase is concerned, the feeding of folic acid or 6-pteridylaldehyde is without effect.