This research proposal is aimed toward elucidation of chronic effects of ethanol on gastric mucus structure and function, and on metabolic activity of gastric mucosa. Since a definite evidence was obtained that ethanol depletes gastric epithelium of its extracellular mucus and intracellular stores of mucus glycoprotein, and produces gastric mucosal injury resulting in the erosions, superficial ulcers, bleeding and chronic gastritis, these studies are aimed toward elucidation of chronic and acute effects of ethanol on various stages of mucus glycoprotein synthesis, modification, elongation of the oligosaccharide chains, secretion, and intracellular storage. The effect of ethanol on mucus glycoprotein synthesis will be evaluated with consideration of the intracellular ratio of NAD+/NADH and endogenous level of prostaglandins, since the change in the redox status is detrimental to the intermediary metabolism, while prostaglandins are involved in the cellular protection. The synthesis and its stages i.e. apoprotein synthesis, acylation, initial glycosylation, elongation, intracellular storage, and secretion will be studied on gastric mucosa cell suspension subjected to short term tissue culture in presence of radiolabeled (3H)proline, (3H)palmitic acid, and (14C)N-acetylgalactosamine. These experiments will show the timetable of 0-fatty acyl incorporation and 0-glycosylation, and will allow to determine the effect of ethanol on the rate of glycoprotein synthesis, secretion, and the intracellular content of glycoprotein and its acylated and glycosylated precursors. The measurement of the rate of incorporation of the (14C)carbohydrate from their respective sugar nucleotides to known glycopeptide acceptors and isolation of the labeled and reduced oligosaccharides will permit to determine whether ethanol affects the rate of glycosylation, the path of glycosylation, and the pool of synthesized apoprotein capable to enter the process of glycosylation with N-acetylgalactosamine. The in vivo studies will allow to follow the effects of ethanol on the metabolic activity of gastric mucosa, and these in vitro to evaluate the effect of ethanol on a one variable at the time. The proposed studies should provide the conclusive evidence with regard to the fundamental understanding of the processes involved in the mucus glycoprotein assembly, their modification in presence of ethanol, as well as it will add to our understanding of the protective role of prostaglandins in gastric mucosa.
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