Ammonia metabolism in normal and portacaval-shunted rats

Advances in Experimental Medicine and Biology
A J Cooper

Abstract

Ammonia is generated from a large number of metabolically important reactions. Despite its central importance in whole body nitrogen homeostasis excess ammonia is neurotoxic and its concentration must be kept low. Ammonia generated in most extrahepatic tissues is detoxified by incorporation into glutamine (amide). This glutamine may be used in a number of biosynthetic reactions (e.g. in pyrimidine synthesis). Alternatively, as a means of maintaining nitrogen balance, glutamine may be released to the blood. Resting skeletal muscle is particularly important 1) as a "sink" for removal of blood ammonia, and 2) as a major source of circulating glutamine. However, during vigorous exercise skeletal muscle may become a net contributor of ammonia to the blood. A few tissues and cell types (e.g. lymphocytes, macrophages, enterocytes, colonocytes, thymocytes, fibroblasts, bone) and tumors exhibit marked rates of glutamine utilization. In the kidney, glutamine is an important source of urinary ammonia. Ammonia generated from 1) the breakdown of nitrogenous substances in the gut, and 2) from the use of glutamine as a metabolic fuel in the small intestine, is taken up by the liver wherein it is detoxified by conversion to urea and to a lesse...Continue Reading

Citations

Nov 28, 2012·Metabolic Brain Disease·Hanan Mardini, Christopher Record
Mar 1, 1994·Journal of Veterinary Internal Medicine·D S Dimski
Oct 25, 2013·Metabolic Brain Disease·Gerald A Dienel, Nancy F Cruz
May 14, 2016·Pediatric Nephrology : Journal of the International Pediatric Nephrology Association·I David Weiner
May 27, 2017·The Biochemical Journal·Stefan Bröer, Angelika Bröer

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