Chromosomal and teratogenic effects of oxygen in the mouse

The effect of oxygen on chromosomes in bone marrow cells and on the early stages of gestation in the mouse were studied. Three groups of male mice were exposed to hyperbaric oxygen at 2, 3 and 4 atm abs. for 1 h, and four other groups breathed pure oxygen at 1 atm abs, for 6, 12, 24 and 48 h respectively. Chromosome were studied after 24 h. In the pure oxygen groups, no significant increase in chromosome aberration was noted, but in the hyperbaric oxygen groups, significant increases in abnormalities (breakage and gap) were noted at 3 and 4 atm abs. (8.0 and 6.7% respectively, P less than 0.05). In another study, four groups of pregnant mice were exposed once to hyperbaric oxygen at either 2 atm abs. for 1 h on the 7th or 8th day of gestation, or 2.5 atm abs. for 2 h on the 5th or 8th day. Six other groups were exposed to 2, 3 and 3.5 atm abs. with either oxygen or air for 1 h daily during first 8 days of gestation. Malformations (umbilical hernia and abnormalities of the coccyx) in the newborn were noted in the groups exposed to hyperbaric oxygen at 2.5 atm abs. for 2 h on the 5th and 8th days of gestation (1/26, 7/42), and all the groups exposed daily to hyperbaric oxygen (1/58, 3/33, 2/24). These findings would seem to indicate a genetic effect of increased oxygen tension in vitro.