Potentiation of atherosclerotic lesions in rabbits by a high dietary level of vitamin E

1. Two experiments were conducted to determine whether or not high dietary levels of vitamin E affect the development of atherosclerotic lesions in aortas of cholesterol-fed (5 g/kg diet) rabbits that were mechanically deendothelialized by balloon catheterization.2. In the first experiment, the aortas of rabbits fed 2000 mg vitamin E/kg diet (i.e. 50-fold their nutritional requirement) for 8 weeks showed no gross morphological differences, either within or outside experimentally damaged areas, from those of rabbits fed the nutritionally adequate control level (40 mg/kg) of the vitamin.3. In the second experiment, rabbits fed 10000 mg vitamin E/kg diet (i.e. 250-fold requirement) for 14–15 weeks showed significantly greater endothelial loss and plaque formation at aortic sites outside of the mechanically damaged area than did controls. Plasma cholesterol levels were very high (9000–14000 mg/1) and were not affected by dietary vitamin E level until 10–12 weeks when they were reduced moderately (18%).4. It is concluded that very high levels of vitamin E can potentiate spontaneous atherosclerotic lesions, and it is suggested that this effect may depend on high cholesterol status.

THE REQUIREMENTS AND ROLE OF POTASSIUM IN OVINE NUTRITION

The role of potassium in ovine nutrition was investigated by using 76 western range lambs in a 56-day feeding trial, a 56-day equalized feeding trial, and two 30-day balance trials. A semipurified ration (.046% potassium) was used and potassium was added as K2CO3. The level of potassium necessary to promote optimum feedlot performance was between 0.3 and 0.5% of the air-dry ration. A marked decrease in appetite was observed in lambs consuming a ration containing 0.1% potassium compared with one containing 0.5% potassium. Lambs receiving a ration containing 0.7% potassium gained significantly (P < 0.05) more body weight than lambs receiving a 0.3% potassium ration in the equalized feeding trial. Results of the balance studies suggested that the daily potassium maintenance requirement was less than 56.1 meq (63.6 mg/kg body weight). Low potassium intakes resulted in significantly (P < 0.05) lower serum levels of potassium and phosphorus with little change in serum sodium, calcium, magnesium, or chloride. Potassium depletion also resulted in a decrease in skeletal and heart muscle potassium and an increase in liver potassium. Apparent intestinal absorption of sodium was impaired by a relatively high dietary level of potassium (94.4 meq daily) while lower levels of potassium resulted in increased urinary sodium losses. Nitrogen balance was decreased when a low level of potassium (13.7 meq daily) was fed; however, potassium intake had no effect on apparent digestibilities of nitrogen, dry matter, or energy.