Ammonia-induced Injury Research Articles

Glutamine protects gastric mucosal cells against ammonia-induced cell death: Implications for the reduction of mucosal injury during infection with H. pylori

Ammonia, a weak base, may play an important role in the pathogenesis of H. pylori disease because it affects cellular function and the viability of gastric epithelial cells. In the brain, liver and kidney, glutamine-metabolic pathways are crucial for scavenging ammonia to protect against cellular injury and death. It is not known, however, whether glutamine can activate similar scavenging pathways in the gastric mucoea. Here, we show that glutamine completely protects against ammonia-induced cell death in gastric mucosal cells. Methods: Viability (crystal violet assay), cell vacuolation (neutral red uptake), and ATP production (luciferase assay) were measured in confluent monolayers of rat gastric mucosal (RGM1) cells in the presence or absence of NH4CI (30 mM). [JH]glutamine and [C]metbytamine uptake into the cells was determined by liquid scintillation. Remits: Treatment with NH,CI caused extensive vacuolation, ATP depletion, and cell death in RGM1 cells. Glutamine, in concentrations from 0.2-20 raM, protected cells against NH,CI-induced cell death. At 20mM glutamine, there was complete inhibition of cell death, a significant reduction in cell vacuolation, and a significant reduction in the amount of ATP depletion. [JH]Glutamine was transported into RGM1 cells. Modification of glutamine metabolism by methionine sulfoximine, a glutamine syothetase inhibitor (lOmM), or aminooxyacetate, an aminotransferase inhibitor (lOmM), protected cells against NH4CI-induced cell death. In contrast, 6-diazo-5-oxo-L-norleucine, a glotaminase inhibitor (2mM) or acivicin, a gamma-glutamyltranspeptidase inhibitor (5raM), had no protective effect on cell death induced by NH4CI. Uptake of a non-metabolized weak base, such as [14C]methylamine, was inhibited in the presence of 20 mU glutamine, suggesting that glutamine also functions to prohibit entry (or facilitate extrusion) of weak bases. Ceecthsiem: Glutamine protects RGM1 cells against death induced by NH~CI in two ways. First, a glutamine-dependent scavenging pathway is used to reduce the intracellular concentration of NH~/NH,* in cells. Second, glutamine acts to inhibit the uptake of NH~'NH4 + into cells. Our results suggest that dietary supplementation with glutamine may be a simple and effective way to protect the gastric mucosa against ammonia-induced injury during H. pylod disease.

Implications of Gastric Topical Bioactive Peptides in Ammonia-induced Acute Gastric Mucosal Lesions in Rats

Background: Ammonia, one of the pathogenic factors in Helicobacter pylori-induced mucosal injury, induces acute mucosal lesions in the rat glandular stomach. Methods: The effect of ammonia administered intragastrically on gastric peptides was investigated in urethane-anesthetized rats. Results: Gastric mucosal lesions were observed 5 min after 0.3% ammonia (4 ml/kg, intragastrically). Immunoreactive endothelin-1 (ET-1) and immunoreactive thyrotropin-releasing hormone (TRH) concentrations in the gastric wall decreased significantly 2 min and 5 min after ammonia, respectively. A significant increase in gastric juice immunoreactive ET-1 and TRH levels was reciprocally observed. The severity of gastric mucosal injury and changes in gastric immunoreactive ET-1 and TRH concentrations were shown to be concentration-dependent 30 min after ammonia. Atropine (5 mg/kg, intraperitoneally, -20 min) prevented ammonia-induced injury accompanied by a block of changes in gastric immunorective ET-1 and TRH concentrations. BQ-485 (ETA receptor antagonist; 2 mg/kg, subcutaneously) also abolished ammonia-induced lesions and gastric immunoreactive TRH changes. Conclusions: These findings suggested that gastric ET-1 and TRH play a role in ammonia-induced gastric mucosal injury mediated via a muscarine and an ETA receptor.

Ammonia-induced injury in pure cultures and natural populations of coliform bacteria

Ammonia-induced injury was investigated in pure cultures of Escherichia coli and Enterobacter aerogenes, and in natural coliform populations obtained from the oligotrophic Luxapallila and the eutrophic Sunflower Rivers in northern Mississippi. Pure cultures were affected by ammonia exposure as indicated by changes in the injury ratio (IR) of CFU on m-T7 agar/CFU on m-Endo agar. Ammonia concentrations between 0 and 20 (mg NH3-N/1) had little or no effect and concentrations between 40 and 80 caused the greatest injury. Natural coliform populations from the oligotrophic river were more prone to ammonia-induced injury than those from the eutrophic river. The results stress the need for the routine use of m-T7 media and the enumeration of injured cells when using the membrane filter procedure to ascertain domestic water quality.

Ammonia-induced injury in pure cultures and natural populations of coliform bacteria.

Ammonia-induced injury was investigated in pure cultures of Escherichia coli and Enterobacter aerogenes, and in natural coliform populations obtained from the oligotrophic Luxapallila and the eutrophic Sunflower Rivers in northern Mississippi. Pure cultures were affected by ammonia exposure as indicated by changes in the injury ratio (IR) of CFU on m-T7 agar/CFU on m-Endo agar. Ammonia concentrations between 0 and 20 (mg NH3-N/1) had little or no effect and concentrations between 40 and 80 caused the greatest injury. Natural coliform populations from the oligotrophic river were more prone to ammonia-induced injury than those from the eutrophic river. The results stress the need for the routine use of m-T7 media and the enumeration of injured cells when using the membrane filter procedure to ascertain domestic water quality.