Utilization of Diammonium Citrate by Adult Rats

Abstract

In the 1st experiment, the utilization of diammonium citrate (DAC) as a non-essential nitrogen source was studied in comparison with glutamic acid. Adult rats fed the amino acid diet containing DAC in place of glutamic acid as a nonessential amino acid maintained their body weights and had nitrogen balances almost equal to those of rats on the glutamic acid containing diets.In the 2nd experiment, DAC-'5N was orally administered after the rats were fed the DAC diet for a month, and the distribution of 15N in the rats' bodies and excreta was examined at the 6th, 12th, 24th and 48th hr after administration.At the 6th hr, 85 % of 15N intake was retained and 60~;;; of 15N intake was found as protein-'5 N. At the 48th hr, retained 15N was 83 % and protein-'5N increased 5 % above that at the 6th hr. The 15N concentration of non-protein fractions was higher and changed more rapidly than that of protein fractions, especially in the blood, liver and small intestine.These results seem to indicate that DAC was utilized by rats fed a diet, in which nonessential amino acids were completely replaced by DAC. Gastrointestinal microbes might hardly play any role in the utilization of dietary non-protein nitrogen under these experimental conditions.Although the use of non-specific nitrogen by hens,'-5) pigs,6-8J and rabbits 9 ,IO) has been studied, there have been no reports on the practical use by monogastric animals.In 1939, the possibility of utilization of ammonium nitrogen by monogastic animals was indicated by Foster et al.,ll) who observed the utilization of ammonia-N for amino acid synthesis in rats by feeding ammonium-'5 N under the condition of low protein diets.Earlier studies '2 -14 ) concluded that the young rats fed diets containing only mixtures of non-specific nitrogen and essential amino acids as the nitrogen sources utilized the nonspecific nitrogen as nitrogen sources for nonessential amino acid synthesis. Ammonium butyrate and ammonium citrate were utilized when non-essential amino acids were replaced by ammonium salts/ 5 -m but the extent of utilization of non-specific nitrogen decreased when the diet contained the non-essential amino acid. This result indicated that the synthesis of carbon skeletons for amino group * Azabu Veterinary College, Fuchinobe, Sagamihara-shi, Japan.acceptors was too slow to supply enough a-keto-glutaric acid (a-KG) which was needed for the synthesis of amino acids. However, the utilization of ammonium salt was not improved even when ammonium salts and a-KG were supplied. 'SJ The purpose of this study was to know the direct evidence to change ammonia in the diet to body proteins and their distributions, and to study the possibility of utilization of nonspecific nitrogen. DAC was chosen as the typical non-specific nitrogens, because it permitted best growth in young rats on nonspecific nitrogens. '3 ,'5,'6) Firstly, changes of body weight and nitrogen balance of rats fed the diet which contained DAC as a nonessential nitrogen source were investigated. Secondly, distributions of DAC-...