Beta-carotene and CNS oxygen toxicity in rats.

Beta-carotenes are reported to be potent free radical quenchers, singlet oxygen scavengers, and lipid antioxidants. Oxygen free radicals that are produced in excess during exposure to oxygen at high pressures and overwhelm the body's normal antioxidant defense systems seem to mediate the hyperoxic insult. We decided to test the possible protective effect against central nervous system oxygen toxicity of a natural beta-carotene composed of equal amounts of the all-trans and 9-cis isomers obtained from the unicellular halotolerant alga Dunaliella bardawil. Rats implanted with chronic cortical electrodes for continuous electroencephalogram monitoring were fed on ground commercial food enriched with natural beta-carotene (1 g/kg diet). On completion of 1 wk of the diet, the rats were exposed to 0.5 MPa oxygen and then their livers were removed for beta-carotene and vitamin A analysis. A significant increase was noted in the latent period preceding oxygen seizures in the group of rats in which the diet was supplemented by natural beta-carotene compared with rats given a normal diet (38.5 +/- 3.4 vs. 16.8 +/- 1.8 min; P < 0.05). Further experiments are required to evaluate the potential benefit of supplementing the diet of divers and patients exposed to high pressures of oxygen with the beta-carotene-rich D. bardawil.