Effect of dietary orotic acid on the levels of liver and blood NAD in rats.

Abstract

The effect of dietary orotic acid on the levels of liver and blood NAD in young rats was investigated. Weanling rats were fed on a nicotinic acid-free, 20% casein diet containing 0% (control diet) or 1% orotic acid (test diet) for 32 days. Retardation of growth, development of fatty liver and enlargement of liver were observed in the test group in comparison with the control group. In the test group, the amounts of quinolinic acid, niacin, NAD and N1-methylnicotinamide, and the activities of quinolinate phosphoribosyltransferase, nicotinamide mononucleotide adenylyltransferase, nicotinamide methyltransferase and NAD synthetase expressed in terms of g liver were significantly decreased compared to the control group. When these values were expressed in terms of whole liver, a significant difference was observed in the content of NAD and the activity of NAD synthetase between the control and the test groups. The activity of aminocarboxymuconate-semialdehyde decarboxylase expressed in terms of whole liver was about 2-fold higher in the test group than in the control group, but was not significantly different. The levels of NAD in blood as well as in liver were significantly lower in the test group than in the control group. Urinary excretions of quinolinic acid, niacin and N1-methylnicotinamide were also reduced in the test group. These results are discussed in the light of the reported effect of orotic acid in lowering the level of ATP in liver.