Chronic hypoxia and glutathione-dependent detoxication in rat small intestine

It has previously been found that chronic O2 deficiency decreases activity of the enzymes of the glutathione (GSH) redox system in the liver. To study the effects of O2 deficiency on intestinal detoxication capacity, pair-fed (16 g food/day) Sprague-Dawley rats were exposed to air (20.9% O2; n = 4) or 10% O2 (n = 4) for 10 days. Animals were killed, and intestinal mucosal homogenate (20% wt/vol) was obtained and assayed for activities of glucose-6-phosphate dehydrogenase (G6PD), GSH peroxidase (GSHPx), GSH disulfide reductase (GSSGRd), and gamma-glutamyl cysteine synthetase (gamma-GCS). Hypoxia decreases activities of GSHPx, GSSGRd, and gamma-GCS by approximately 50%, which suggests compromised detoxication. A proximal-to-distal reduction in enzymatic capacity indicates impairment of detoxication may be more pronounced in the distal intestine. G6PD, a key enzyme in NADPH production, remains unchanged. Urinary malondialdehyde was also monitored. Hypoxic rats exhibited a threefold increase in thiobarbituric acid-reactive substance, consistent with a generalized oxidative stress in these animals. Taken together, the results indicate that chronic hypoxia promotes tissue oxidative stress and impairs the ability of the enterocyte to metabolize ingested oxidants.