Arginine - Nutrition
1. What is Arginine?
Arginine is an essential amino acid for dogs and cats. It is classified as a gluconeogenic amino acid and contains a positively charged nitrogen side chain that can be used as a binding site for other molecules. Dietary arginine is absorbed by a dibasic amino acid transporter in the small intestine (particularly the jejunum) and plasma arginine is actively reabsorbed in the proximal tubule of the kidney. Species that do not require dietary arginine (such as humans) are able to endogenously synthesise adequate amounts of this amino acid through the conversion of glutamate into ornithine; ornithine is ultimately converted into arginine in the urea cycle through the activity of pyrroline-5-carboxylate synthase and ornithine aminotransferase. Low activity these enzymes are found in dogs and cats. Dogs and cats have an absolute requirement for dietary arginine.
2. Why is it Important?
Arginine plays a critical role in the detoxification of ammonia, resulting from the turnover and breakdown of proteins. It is an important intermediate in the urea cycle which converts ammonia to urea. In the cats the arginine dietary protein in order to handle the increased need for detoxifying ammonia released from amino acid catabolism a. Cats are also highly sensitive to dietary arginine deficiency, feeding an arginine free diet to cats can result in hyperammonemia and death within a few hours.
3. Roles in the Body
Arginine is a structural component of proteins; serves as a key substrate for the detoxification of ammonia; stimulates the release of hormones, such as insulin, glucagon, and gastrin; and is a precursor to nitric oxide (NO), which is used as a cell signalling mediator.
4. Consequences of Arginine Deficiency
Puppies fed an arginine deficient diet containing adequate total protein will experience a decreased food intake and hyperammonemia resulting in vomiting and ptylism, with an increase in urinary orotic acid excretion and muscle tremors. There are also reports of puppies developing cataracts after being fed an arginine-free milk replacer. Feeding an arginine deficient diet to adult dogs results in decreased in food intake. An inherited defect in the transporter for dibasic amino acids can also occur in certain breeds of dog resulting in poor absorption of arginine (as well as the other dibasic amino acids cystine, ornithine, and lysine) from the intestinal mucosa and poor reabsorption in the renal tubule.
Feeding of an arginine deficient diet to kittens results in diarrhoea, weight loss, food refusal, ataxia, hyperammonemia, and urinary orotic aciduria. Feeding a diet that has no arginine but contains substantial levels of other amino acids can result in death within a few hours.
There are no studies on either acute or chronic toxicity related to feeding high doses of arginine to dogs and no reports of safe upper limits. Kittens fed purified diets containing arginine at 5-10 times above the requirement had a decrease in growth rate, but immediate adverse effects were not noted. Toxicity studies in adult cats are lacking.
6. Dietary Sources
Sufficient arginine is found in plant and animal protein sources, such as muscle meat, eggs, dairy protein (i.e., casein), cereal grains, and pulses (i.e., legumes).
7. Diagnosing Arginine Deficiency
Diagnosis of arginine deficiency is based on fasted plasma amino acids and the presence of urinary orotic acid.
- Burns RA, et al. Arginine: An Indispensable Amino Acid for Mature Dogs. J Nutr 1981; 111:1020-1024.
- Morris JG. Nutritional and Metabolic Responses to Arginine Deficiency in Carnivores J Nutr 1985;115:524-531.
- Taylor TP, et al. Increasing dispensable amino acids in diets of kittens fed essential amino acids at or below their requirement increases the requirement for arginine. Amino Acid 1997;13:257-272.
- Morris JG and Rogers QR. Ammonia intoxication in the near-adult cat as a result of a dietary deficiency of arginine. Science 1978 Jan 27;199(4327):431-2
- National Research Council (NRC). Protein and Amino Acids. In Nutrient Requirements for Dogs and Cats. 2006 Washington, DC: National Academies Press p. 120-122.
- Ha YH, et al. Arginine requirement in immature dogs. J Nutr 1978;108:203-210.
- Czarnecki GL, et al. Urea cycle function in the dog with emphasis on the role of arginine. J Nutr 1984;1115:743-752.
- Glaze MB and Blanchard GL. Nutritional cataracts in a Samoyed litter. JAAHA 1983;19:951-954.
- Martin CL and Chambreau T. Cataract production in experimentally orphaned puppies fed a commercial replacement for bitch’s milk. JAAHA 1983;18:115-119.
- Vainisi SJ, et al. Nutritional cataracts in Timber wolves. JAVMA 1981;179:1175-1180.
- Ranz D, et al. Nutritional lens opacities in two litters of Newfoundland dogs. J Nutr 2002;132:1688S-1689S.
- Taylor TP, et al. Optimizing the pattern of essential amino acids as the sole source of dietary nitrogen supports near maximal growth in kittens. J Nutr 1996;126:2243-2252.