Suppression of hepatic prostaglandin F2 alpha in rats by dietary alpha-tocopherol acetate is independent of total hepatic alpha-tocopherol

No inhibition of gamma-glutamyl transpeptidase-positive foci by vitamin E with or without phenobarbital

The effect of vitamin E on gamma-glutamyl transpeptidase-positive foci, with or without phenobarbital, was investigated. Groups of six female Sprague-Dawley rats were initiated with diethylnitrosamine (15 mg/kg) at 24 hours of age. After weaning, they were fed diets with 10% (wt/wt) fish oil; the diets contained 0, 5,000 or 15,000 ppm vitamin E supplementation with or without phenobarbital (500 ppm) for six months. Phenobarbital significantly increased liver weight and liver weight as a percentage of body weight (p < 0.05), suggesting a liver hypertrophic effect of phenobarbital. Phenobarbital significantly decreased hepatic phospholipid arachidonate, eicosapentaenoate, and docosahexaenoate (p < 0.05); this may indicate that phenobarbital stimulates phospholipase A2 activity and results in the increased release of polyunsaturated fatty acids from phospholipids and the decrease of hepatic phospholipid polyunsaturated-to-saturated fat ratio. In rats fed phenobarbital, hepatic vitamin E content was lower than in rats fed no phenobarbital; this suggests that phenobarbital causes oxidative stress or induces enzymes that metabolize the vitamin. Phenobarbital exposure significantly increased hepatic prostaglandin F2 alpha and glutathione S-transferase activity (p < 0.05). Vitamin E did not influence hepatic gamma-glutamyl transpeptidase-positive foci area and number with or without phenobarbital, and phenobarbital showed a strong promoting action on enzyme-altered hepatic foci.

Effects of vitamin E deficiency and dietary linoleate on serum thromboxane synthesis in male sprague-dawley rats

The aim of the present study was to examine whether vitamin E deficiency and dietary linoleate had additive or synergistic effects on serum thromboxane (TX) status and therefore on thrombogenesis. Eight groups of five male weaning Sprague-Dawley rats were fed semipurified diets containing 3.5 or 18.4% of energy from linoleate (en% linoleate) and 0, 100, 5000, 15,000 ppm vitamin E for 8 weeks. Rats fed no vitamin E had the lowest serum vitamin E while rats fed 15,000 ppm vitamin E had the highest serum vitamin E (p < 0.05). Serum 18:2, n-6 (linoleic acid; LA) and 20:4, n-6 (arachidonic acid; AA) were significantly greater in the 18.4 en% linoleate group than in the 3.5 en% linoleate group (p < 0.05). Serum TXA2, measured as its stable metabolite TXB2, was significantly greater in the vitamin E-deficient rats than in the vitamin E-adequate and vitamin E-supplemented rats (p < 0.05). Serum lipid peroxidation, measured as thiobarbituric acid reactive substances (TBARS), was significantly greater in the 0 and 100 ppm vitamin E groups than in the 5000 and 15,000 ppm vitamin E groups (p < 0.05). No interaction between dietary linoleate and vitamin E deficiency on serum TX status was found. However, it seemed that vitamin E deficiency had a more potent effect on TX synthesis than dietary linoleate. The result suggested that vitamin E deficiency may be prothrombogenic via its effect on TX synthesis.