ABSTRACT
Background Reactive oxygen species (ROS) have been implicated in the turnover of epithelial cells in the rat intestine. The metabolism of ethanol generates ROS, which are implicated in cellular injury, but the levels of lipid peroxidation in intestine in chronic alcoholism are unknown. Aim To investigate the effects of ethanol ingestion on lipid peroxidation, and anti- and pro-oxidant enzyme systems in enterocytes across the crypt–villus axis in intestine. Methods Wistar rats (90–100 g) were administered 1 mL of 30% ethanol daily for 39 days. Intestinal epithelial cells were isolated in fractions. Malondialdehyde levels, and activities of glutathione-S-transferase (GST), glutathione reductase (GR), superoxide dismutase (SOD) and catalase were determined in various cell fractions. Incorporation of H3- thymidine into DNA of enterocytes was also determined. Results Lipid peroxidation was elevated by two- to threefolds in both villus and crypt cells in ethanol-fed animals compared to controls. The activities of GST and GR were four- to six-folds higher in villus tip cells compared to crypt base cells. The activities of SOD and catalase were five- to seven-fold higher in crypt base cells compared to villus tip cells. Ethanol feeding elevated the activities of SOD (76-190%) and catalase (20-150%) in enterocytes all along the crypt–villus axis compared to the controls. H3 thymidine incorporation into DNA of enterocytes was reduced by half in ethanol-fed rats compared to controls. Conclusions There is a gradient in the concentration of lipid peroxides in enterocytes across the crypt–villus axis, being high at the villus tip and low at the crypt base in the rat intestine. Ethanol feeding enhanced lipid peroxidation in both villus and crypt cells.
ABSTRACT
Intestinal epithelium secretes novel unilamellar membranes having characteristics similar to lung surfactants and thus has been named Surfactant-like particles (SLP). The chemical analysis of the membranes revealed cholesterol/phospholipid molar ratio of 0.68-0.78, which is much distinct from that of the underlying microvillus membranes (1.34-1.49). The membrane contains 4-6 proteins with a molar weight of 30-120 kDa and is enriched with alkaline phosphatase, contains low amounts of disaccharidases but no Na+, K(+)-ATPase activity. The secretion of SLP is stimulated by fat feeding. Chronic ethanol ingestion also induces the formation of SLP in rat intestine. A number of physiological functions have been attributed to SLP, which include: (i) as a protective lubricant in intestinal lumen, (ii) a role in triacylglycerol transport, (iii) as a vehicle for the transport of luminal proteins into blood, (iv) as a stratum for the adhesion of microorganisms in intestinal lumen, and (v) a role in trans-signalling mechanism across the basolateral surface of enterocytes.