Transport of Urea and Ammonia Production in the Human Colon

Ammonia inhibits cAMP-regulated intestinal Cl- transport. Asymmetric effects of apical and basolateral exposure and implications for epithelial barrier function.

“…The normal colon absorbs substantial quantities of ammonia, approximately 250 mmol daily, and is the major source of the ammonia found in peripheral blood (10,33,34). Thus, regardless of the precise permeability properties of crypt cells alone (native or T84 model crypt cells), the epithelium as a whole clearly does not behave as an absolute permeability barrier to ammonia.…”

Ammonia production by intestinal bacteria: the effects of lactose, lactulose and glucose

“…The origin of colonic ammonia is uncertain; urea has been suggested as the main source (Wolpert, Phillips and Summerskill, 1971) but Vhce et al (1976) have shown that considerable amounts of ammonia, in excess of those normally found in faeces, were generated by bacteria from non-urea sources in an in-vitro faecal incubation system. Addition of fermentable substrate-lactulose, glucose, mannitol or sorbitol-to this system caused a decrease in the ammonia concentration (Vince, Killingley and Wrong, 1978).…”

Carbon Dioxide Formation and Elimination in Man

“…The breakdown of urea normally takes place in the intestine (28,29,56,57,58,59,60) by means of urease-producing bacteria (61,62) which colonize the newborn infant's intestine, which initially after birth is sterile. This colonization is considered to take place during the first days of life, but according to my hypothesis it is delayed, inhibited or in some other way insufficient in those infants who develop respiratory insufficiency leading to sudden infant death.…”