Effects of beta-carotene and retinyl palmitate on corn oil-induced superoxide dismutase and catalase in rats.

The present study was undertaken to determine the effects of beta-carotene on corn oil-induced superoxide dismutase and catalase. Six groups of male Buffalo rats were fed the following diets for 6 wk: a control diet containing recommended levels of beta-carotene and retinyl palmitate, a retinol diet containing 10 times the recommended level of retinyl palmitate, and a beta-carotene diet containing 10 times the recommended levels of beta-carotene and adequate levels of retinyl palmitate. Each vitamin combination was fed with either 5% (wt/wt) corn oil (low fat) or 20% corn oil (high fat). Plasma total beta-carotene levels were highest in the beta-carotene groups. Levels varied inversely with the level of fat in the control group and directly with fat in the beta-carotene group. Transport of beta-carotene appeared to parallel that of cholesterol in that 36 and 35%, respectively, were associated with the low density lipoprotein fraction. Accumulation of beta-carotene in the liver was apparent from the observation that levels in liver were much higher than those in plasma. Superoxide dismutase activity was much lower in the beta-carotene groups than in the retinol groups, irrespective of level of fat, and catalase activity was also lower in the beta-carotene group, but it was in proportion to the level of fat. These findings suggest that beta-carotene functions as an antioxidant in vivo.