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 t he development of intestinal damage during perinatal development. The aim o f this study was to investigate the histopathology of the intestine in the developing chick embryo after exposure to repetitive hypoxia and recovery u nder two different conditions: normoxic and hyperoxic (60% O-2). Methods: Chick embryos were exposed to 5 minutes of hypoxia. This was repea ted six times with a recovery period of 15 minutes under normoxic condition s (21% O-2) for chick embryos in test group 1 (TG1) and under hyperoxic con ditions (100% O-2) for chick embryos in test group 2 (TG2). from day 11 unt il day 20. Chick embryos that recovered under hyperoxic conditions (100%,) were previously incubated under hyper oxic conditions (60%, for 24 hours). Histologic evaluation of the ileum was performed at different times after t he 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 vi llus capillaries (10% in TG1 and 15% in TG2), necrosis in the top of the vi lli (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 grou p, were only found in chick embryos that were studied 2 hours after the int erventions. Furthermore, recovery under hyperoxic conditions did not cause more intestinal damage compared with recovery under normoxic conditions.