Urea cycling and ammonia absorption in vivo in the digestive tract of the rat

Demigné, Christian; Rémésy, Christian

doi:10.1051/rnd:19790633

Cited by 35 publications

(19 citation statements)

References 17 publications

(6 reference statements)

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“…Normally no urea is present in the intestine and faeces of CY animals (Ducluzeau et al, 1966;Wrong, 1971;Demigne & Remesy, 1979). It has been shown (Ducluzeau et al, 1966;Moreau, Ducluzeau & Raibaud, 1976) that association with ureolytic bacteria brings down the urea content in the faeces to zero, whilst the ammonia content Increases.…”

Section: Discussionmentioning

confidence: 99%

Intestinal accumulation of urea in germ-free animals - a factor in caecal enlargement

Juhr¹,

Ladeburg²

1986

Lab Anim

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SummaryTo examine the connection between caecal size and urea concentration in the caecal contents urease inhibition was tested in conventional animals and urea and urease were administered to germ-free rats and mice. Administration of alloxan and barbituric acid and immunization with urease led to slightly larger caeca in conventional animals. Neomycin treatment caused a clear enlargement of the caecum.In germ-free animals urease administration led to a reduction in the caecal size, whereas urea in the drinking water caused enlargement. The urea concentration and the urease activity in the caecal contents correlated well with the caecal weights. Keywords: Muridae; Germ-free life; Caecum; UreaPrevious tests had revealed that the feeding of urea to germ-free (GF) rats increases the relative caecal weight, whereas urease administration in the drinking water leads to a reduction of the enlarged caecum (Juhr, 1985). The hypothesis of a connection between urea accumulation in the intestinal tract of GF animals and caecomegaly was examined in further tests with rats and mice by administration of urease inhibitors (alloxan, barbituric acid) and neomycin and by immunization with urease in conventional (CY) animals, and also by administration to GF rats and mice of urease and urea in the drinking water. Materials and methods AnimalsMale GF Han:WIST (Wistar) rats and male GF Han:NMRI mice and CY animals of both strains from the stock of the Institute for Laboratory Animal Science were used. The GF animals were kept according to gnotobiotechnical standards (Heine, 1968) in isolators of the Trexler type (Metall und Plastik, Radolfzell, FRG). The CY animals were kept in an animal laboratory of the barrier type.Food (Altromin 1324, fortified: Altromin Spezialfutterwerk, Lage, FRG) and water (tap water) for the GF animals were autoclaved at 135°C for 5 min

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Section: Discussionmentioning

confidence: 99%

Intestinal accumulation of urea in germ-free animals - a factor in caecal enlargement

Juhr¹,

Ladeburg²

1986

Lab Anim

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“…Table 6 Bacterial N and 15 N in large intestine after a dose of 15 N-urea at the end of 9 days feeding period in growing rabbits D-mannitol increases nitrogen utilization in rabbits bacterial growth (Regoeczi et al, 1965). The urea that is transferred from the blood to the large intestine is degraded to ammonia by bacterial urease and subsequently used for bacterial protein synthesis (Demigné and Ré mé sy, 1979;Viallard, 1984;Sarraseca et al, 1998). In the present study, the addition of mannitol to the diet decreased the concentration of cecal ammonia N (P , 0.05), but increased the 15 N enrichment of cecal ammonia N (P , 0.01).…”

Section: Weight Of Gutmentioning

confidence: 99%

Transfer of blood urea nitrogen to cecal microbial nitrogen is increased by mannitol feeding in growing rabbits fed timothy hay diet

Xiao

Jin

et al. 2012

Animal

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The presence of the fermentable sugar D-mannitol in the diet improves nitrogen (N) utilization in rabbits. To clarify the mechanism by which D-mannitol improves N utilization, we studied the effect of D-mannitol on the fate of blood urea N in growing rabbits. Growing rabbits received a control diet or a diet containing D-mannitol, which were formulated by adding 80 g/kg glucose or D-mannitol to timothy hay. After 9 days of feeding of the experimental diets, 15 N-urea was administrated intravenously under anesthesia 1 h before slaughter. The blood urea level (concentration of both urea N (43.6% of the control group (CG), P , 0.05) and 15 N (95% of the CG, P , 0.05) in blood serum) was reduced in the mannitol group. The concentration and amount of N, and 15 N atom % excess in the contents of the cecum and colon were higher (P , 0.05) in the rabbits fed the mannitol diet than in rabbits fed the control diet, especially in the cecum. The consumption of mannitol caused bacterial proliferation in the cecum characterized by marked short-chain fatty acid production (165% of the CG, P , 0.05), decreased cecal ammonia N (73% of the CG, P , 0.05) and elevated cecal bacterial N (150% of the CG, P , 0.05). On the other hand, addition of D-mannitol to the diet decreased N (80% of the CG, P , 0.05) and 15 N (77% of the CG, P , 0.05) excretion in the urine. These results indicate that D-mannitol increases the transfer of blood urea N to the large intestine, where it is used for bacterial N synthesis.Keywords: fermentable sugar, D-mannitol, nitrogen, growing rabbits ImplicationsCecotrophy allows rabbits to reingest microbial products from the cecum as cecotrophs. Cecotrophy has considerable significance for nitrogen (N) metabolism in rabbits. A previous study indicated that as a fermentable sugar, D-mannitol increases N utilization through cecotrophy by deceasing urinary N excretion in rabbits. In the present study, we clarified the possible mechanism by which D-mannitol improves N utilization in growing rabbits. The results indicate that D-mannitol can be used as a cecal microbial stimulator to promote the utilization rate of dietary N in rabbits fed a diet of timothy hay. Moreover, it might aid in reducing the N load passed on to the environment. IntroductionIt is well documented that fermentable carbohydrates can increase urea flux from the blood to the digestive tract and alter fermentation in the large intestine of rats (Ré mé sy and Demigné, 1989;Younes et al., 1995b;Henningsson et al., 2002). In rabbits, a considerable portion of endogenous urea is transferred to the alimentary tract (Regoeczi et al., 1965), and the exchange between blood urea nitrogen (N) and cecal ammonia N is well established Parker, 1985a and1985b). However, the exact fate of blood urea in rabbits fed a diet containing fermentable sugar remains unclear.Urea, as an end product of ammonia and protein metabolism, is synthesized in the liver of mammals and passed into the blood stream (Stewart and Smith, 2005). Most of the blood urea is eliminated ...

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“…Normally, ammonia ranges from 15-50 mmol/kg of whole feces or about 3-44 mmol/I of luminal fluid (8). Fecal ammonia is derived from bacterial degradation in the large bowel of endogenous urea from tissue fluid and also of proteins and amino acids that escape digestion and absorption in the small intestine (8,9). The urea concentration in blood depends primarily on protein intake, urine volume, and the functional state of the kidney.…”

Section: Determinants Of Colonie Luminal Phmentioning

confidence: 99%

Determinants and consequences of colonic luminal pH: Implications for colon cancer

Newmark

Lupton

1990

Nutrition and Cancer

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Epidemiological data suggest that increased risk of colon cancer is correlated with a higher fecal pH. Although some experimental studies have shown a protective effect against experimentally induced colon cancer by acidifying colonic contents, others have shown that a more acidified colonic content is associated with increased cell proliferation and enhanced tumorigenesis. It is now clear that simply acidifying colonic contents will not consistently result in decreased tumorigenesis. Perhaps the key is how colonic contents are acidified--a decrease in base production or an increase in acid production. Or, more important than luminal pH itself, may be a factor affected by changes in hydrogen ion concentration. This paper reviews the determinants of colonic luminal pH and their dietary sources and discusses important physiological consequences of modifying the pH of colonic contents.

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Urea cycling and ammonia absorption in vivo in the digestive tract of the rat

Cited by 35 publications

References 17 publications

Intestinal accumulation of urea in germ-free animals - a factor in caecal enlargement

Intestinal accumulation of urea in germ-free animals - a factor in caecal enlargement

Transfer of blood urea nitrogen to cecal microbial nitrogen is increased by mannitol feeding in growing rabbits fed timothy hay diet

Determinants and consequences of colonic luminal pH: Implications for colon cancer

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