[The effect of beta-carotene on the cytoplasmic membrane lipids of cells in rats under chronic gamma irradiation].

Chronic gamma irradiation of rats at a dose rate of 12.9 rad/day for 155 days (total dose 20 Gy) did not change the cholesterol level in the brush border membrane of the small intestine. Maintenance of rats on a beta-carotene-enriched diet (daily throughout the irradiation period, at a diurnal dose of 3 mg/kg body weight produced an increase in cholesterol levels in the small intestinal brush border membranes. The phospholipid level after gamma irradiation alone did not change, but it was increased in gamma-irradiated rats fed with carotene, this increase being most pronounced for sphingomyelin. Beta-carotene decreased the cholesterol/phospholipid ratio in the brush border membrane of irradiated rats. Activation of lipid synthesis (as seen from inclusion of 2-14C-acetate in the epitheliocyte lipids of irradiated animals) and no influence of beta-carotene on the inclusion of the label in small intestine epitheliocytes of irradiated animals have been revealed. In the presynaptic membranes of brain nerve endings, chronic gamma irradiation of animals produced a deep fall of cholesterol and phospholipid levels. Also, a tendency was revealed for stimulation of transport of the neurotransmitter amino acids GABA and L-glutamate across the presynaptic membranes of nerve endings. Beta-carotene normalized the phospholipid and cholesterol levels in brain presynaptic membranes of irradiated rats, as well as decreased L-glutamate transport. It is assumed that the modifying and normalizing effects of beta-carotene on the lipid exchange of plasma membranes upon chronic irradiation of animals and permanent introduction of the drug are associated with the radioprotector activity of beta-carotene.