Modulations of rabbit erythrocyte ATPase activities induced by in vitro and in vivo exposure to ethanol

The Influence of Alcohol Consumption on Intestinal Nutrient Absorption: A Comprehensive Review

Chronic alcohol use has been attributed to the development of malnutrition. This is in part due to the inhibitory effect of ethanol on the absorption of vital nutrients, including glucose, amino acids, lipids, water, vitamins, and minerals within the small intestine. Recent advances in research, along with new cutting-edge technologies, have advanced our understanding of the mechanism of ethanol's effect on intestinal nutrient absorption at the brush border membrane (BBM) of the small intestine. However, further studies are needed to delineate how ethanol consumption could have an impact on altered nutrient absorption under various disease conditions. Current research has elucidated the relationship of alcohol consumption on glucose, glutamine, vitamins B1 (thiamine), B2 (riboflavin), B9 (folate), C (ascorbic acid), selenium, iron, and zinc absorption within the small intestine. We conducted systematic computerized searches in PubMed using the following keywords: (1) "Alcohol effects on nutrient transport"; (2) "Alcohol mediated malabsorption of nutrients"; (3) "Alcohol effects on small intestinal nutrient transport"; and (4) "Alcohol mediated malabsorption of nutrients in small intestine". We included the relevant studies in this review. The main objective of this review is to marshal and analyze previously published research articles and discuss, in-depth, the understanding of ethanol's effect in modulating absorption of vital macro and micronutrients in health and disease conditions. This could ultimately provide great insights in the development of new therapeutic strategies to combat malnutrition associated with alcohol consumption.

Moderate Alcohol Consumption Inhibits Sodium-Dependent Glutamine Co-Transport in Rat Intestinal Epithelial Cells in Vitro and Ex Vivo

Malnutrition is present in chronic alcoholics. However, how moderate alcohol consumption affects the absorption of nutrients like glutamine has not been investigated. Glutamine, an amino acid, is vital to gastrointestinal health. Glutamine is absorbed via sodium-dependent glutamine co-transport (B0AT1; SLC6A19) along the brush border membrane of absorptive villus cells. Rat intestinal epithelial cells (IEC-18) and sixteen-week-old Sprague Dawley rats were administered the equivalent of a 0.04% blood alcohol content of ethanol (8.64 mM; 2 g/kg) to investigate the effect of moderate alcohol on sodium-glutamine co-transport. Sodium-dependent ³H-glutamine uptakes were performed to measure B0AT1 activity. Inorganic phosphate was measured as a function of Na-K-ATPase activity. Protein expression was analyzed by immunohistochemical and Western blot analysis. Ethanol significantly inhibited sodium-dependent glutamine absorption and Na-K-ATPase activity in enterocytes in vitro and ex vivo. Kinetic studies suggested that the mechanism of inhibition was due to decreased maximal rate of uptake (V_max) of the B0AT1 co-transporter, corresponding to decreased B0AT1 protein expression and secondary to an inhibited sodium-gradient at the cellular level in vitro and ex vivo. In all, moderate ethanol significantly inhibited glutamine absorption at the level of decreased B0AT1 expression at the brush border membrane and a reduced sodium gradient, which may contribute to malnutrition present in chronic alcoholics.

The activity of erythrocyte and brain Na+/K+ and Mg2+-ATPases in rats subjected to acute homocysteine and homocysteine thiolactone administration

Hyperhomocysteinemia is associated with various pathologies including cardiovascular disease, stroke, and cognitive dysfunctions. Systemic administration of homocysteine can trigger seizures in animals, and patients with homocystinuria suffer from epileptic seizures. Available data suggest that homocysteine can be harmful to human cells because of its metabolic conversion to homocysteine thiolactone, a reactive thioester. A number of reports have demonstrated a reduction of Na+/K+-ATPase activity in cerebral ischemia, epilepsy and neurodegeneration possibly associated with excitotoxic mechanisms. The aim of this study was to examine the in vivo effects of D,L-homocysteine and D,L-homocysteine thiolactone on Na+/K+- and Mg2+-ATPase activities in erythrocyte (RBC), brain cortex, hippocampus, and brain stem of adult male rats. Our results demonstrate a moderate inhibition of rat hippocampal Na+/K+-ATPase activity by D,L-homocysteine, which however expressed no effect on the activity of this enzyme in the cortex and brain stem. In contrast, D,L-homocysteine thiolactone strongly inhibited Na+/K+-ATPase activity in cortex, hippocampus and brain stem of rats. RBC Na+/K+-ATPase and Mg2+-ATPase activities were not affected by D,L-homocysteine, while D,L-homocysteine thiolactone inhibited only Na+/K+-ATPase activity. This study results show that homocysteine thiolactone significantly inhibits Na+/K+-ATPase activity in the cortex, hippocampus, and brain stem, which may contribute at least in part to the understanding of excitotoxic and convulsive properties of this substance.

Na⁺,K⁺-ATPase as the Target Enzyme for Organic and Inorganic Compounds

This paper gives an overview of the literature data concerning specific and non specific inhibitors of Na⁺,K⁺-ATPase receptor. The immobilization approaches developed to improve the rather low time and temperature stability of Na⁺,K⁺-ATPase, as well to preserve the enzyme properties were overviewed. The functional immobilization of Na⁺,K⁺-ATPase receptor as the target, with preservation of the full functional protein activity and access of various substances to an optimum number of binding sites under controlled conditions in the combination with high sensitive technology for the detection of enzyme activity is the basis for application of this enzyme in medical, pharmaceutical and environmental research.