EFFECTS OF HYPERBARIC-OXYGEN ON RAT EMBRYOS

The aim of the study was to investigate the toxic effects of hyperbari c oxygen (HBO) on rat embryos. Two groups of Fischer pregnant rats wer e exposed to oxygen at pressures of 324 and 426 kPa for 90 min per day for 5 consecutive days (8-12 days of gestation). The third group was exposed to normobaric oxygen for 12 h on the eighth day of gestation. Two control groups were used; the first was comprised of intact and th e second of sham-treated animals. The HBO treatment did not significan tly affect maternal weight gain or reduce litter size, nor did it indu ce any embryonic abnormalities. However, the fetal body weight was red uced and the placental weight increased in the groups exposed to HBO a t pressures of 324 and 426 kPa. When female fetuses which had been exp osed to oxygen at 324 or 426 kPa were compared to the intact control g roup, a reduction in wet weights of 9.2 (p < 0.05) and 12.1% (p < 0.01 ), respectively, was noted. Male fetuses exposed to oxygen at 324 and 426 kPa displayed a reduced body weight of 11.7 (p < 0.01) and 16.6% ( p < 0.01), respectively. Placental weight was increased by 18.9 (p < 0 .01) and 23.6% (p < 0.0 in the groups exposed to oxygen at 324 and 426 kPa, respectively. These data suggest that HBO, either at 324 or 426 kPa, is not potent at inducing malformations and that the largest embr yotoxic effects are upon fetal body weight and placental weight. Howev er, the histological examination of placentas revealed alterations in labyrinthine blood vessels and a statistically significant thickening of the placental barrier. In conclusion, this study suggests that tran sient interference with normal placentation is probably sufficient to cause permanent maldevelopment of the placenta and embryo.