QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Hassan, A. S. Articles by Milner, J. A. Search for Related Content PubMed PubMed Citation Articles by Hassan, A. S. Articles by Milner, J. A.

Orotic Aciduria and Increased Nitrogen Catabolism in Rats^{1, 2,}

Department of Food Science, University of Illinois, Urbana, Illinois 61801

In vitro incorporation of [¹⁴C]bicarbonate into orotic acid by rat liver slices was used to study the rate of orotic acid (OA) biosyn-thesis in the presence of physiological (0.73 mM) and saturation concentrations (5 mM) of NH₄Cl. The influence of body size on OA synthesis in rats fed purified L-amino acid diets with (C) or without (-Arg) was examined. OA biosynthesis was significantly greater at both NH₄Cl concentrations examined in liver slices obtained from -Arg rats for all sizes of rats. A linear decrease (r = 0.92) in OA synthesis as a function of body size was observed for rats fed either of the diets. The rate of OA biosyn-thesis was also found to increase linearly (r = 0.98) in livers from rats fed increasing dietary protein when determined by incubation with physiological concentrations of NH₄Cl. OA biosynthesis was also found to increase with increase in length of fasting. Alteration in urinary OA and urea confirm these rates of synthesis. These results support the hypothesis that when the urea cycle is overtaxed, carbamyl phosphate (CP) synthesized intramitochondrially by CP synthetase I may be shunted into pyrimidine biosynthesis.

KEY WORDS: • arginine • protein • orotate • urea cycle • starvation

¹ These investigations were supported by Public Health Service research grant from the National Institute of Health, National Institute of Arthritis, Metabolism, and Digestive diseases (AM 19294).

² Submitted in part to the annual meetings of the Federation of American Societies for Experimental Biology, April, 1979.

Manuscript received 12 March 1979.