The effect of dietary vitamin E and ß-carotene on oxidation processes in the rat testis

The effects of dietary vitamin E and ß-carotene were studied on enzymes involved in arachidonic acid metabolism and other related enzymes in the rat testis. Groups of rats were fed various soybean oil-based semi purified diets. Group 1 was fed a vitamin E-supplemented diet (+E-ß); Group 2 was fed a ß-carotene-supplemented diet (-E+ß); Group 3, the control group (-E-ß) was fed a vitamin E-deficient diet; and Group 4, the standard diet group (S), was fed vitamin E plus ß-carotene-standard diet. Soybean oxidized oil was added to the three diet groups - (+E-ß), (-E+ß) and (-E-ß), whereas the diet of S group contained non-oxidized oil. After 8 weeks rats were killed, blood and testis samples were collected for biochemical determinations. Vitamin E deficiency caused significant increase in testis thiobarbituric acid value and activities of testis NADPH oxidase, testis 15-lipoxygenase and in plasma pyruvate kinase. In contrast, significant decreases were observed in activity of testis prostaglandin synthetase, compared with antioxidant-supplemented diet groups. We also found a significant increase in 15-lipoxygenase activity in (-E+ß) diet group, compared with (-E-ß) diet group. Fatty acid analysis of testis parenchyma indicated decrease in palmitate (16:0) and arachidonate (20:4(n-6)), and increase in oleate (18:1(n-6)) linoleate (18:2(n-6)) and linolenate (18:3(n-3)), when compared (-E-ß) diet group with vitamin E-supplemented diet groups. The results suggest that dietary vitamin E has a role in both enzymatic and non-enzymatic peroxidation of polyunsaturated fatty acids in the testis.