Extent of intestinal damage in the developing chick embryo after repetitive hypoxia under normoxic or hyperoxic conditions.

BACKGROUND: Episodes of hypoxia and reperfusion play an important role in the development of intestinal damage during perinatal development. The aim of this study was to investigate the histopathology of the intestine in the developing chick embryo after exposure to repetitive hypoxia and recovery under two different conditions: normoxic and hyperoxic (60% O2). METHODS: Chick embryos were exposed to 5 minutes of hypoxia. This was repeated six times with a recovery period of 15 minutes under normoxic conditions (21% O2) for chick embryos in test group 1 (TG1) and under hyperoxic conditions (100% O2) for chick embryos in test group 2 (TG2), from day 11 until day 20. Chick embryos that recovered under hyperoxic conditions (100% O2) were previously incubated under hyperoxic conditions (60% O2 for 24 hours). Histologic evaluation of the ileum was performed at different times after the interventions (2, 4, 8, 16, and 24 hours). RESULTS: In both test groups, only chick embryos older than 19 days showed intestinal damage. Intestinal histology on day 19 showed vasodilation of villus capillaries (10% in TG1 and 15% in TG2), necrosis in the top of the villi (29% in TG1 and 30% in TG2), and necrosis with preservation of base of the crypts (2% in TG1) and transmucosal necrosis (2% in TG2). CONCLUSIONS: Significant histologic changes, compared with the control group, were only found in chick embryos that were studied 2 hours after the interventions. Furthermore, recovery under hyperoxic conditions did not cause more intestinal damage compared with recovery under normoxic conditions.