Effects of dietary fats, alpha-tocopherol and beta-carotene supplementation on aortic ring segment responses in the rat.

We examined the effects of vitamin supplement on the vascular smooth muscle response of rats fed four different oil diets, after a 20-day feeding period. Male Sprague Dawley rats were fed diets containing 15% of each hazelnut, corn, olive or fish oils, with/without 30 mg/kg beta-carotene and 500 mg/kg dl-alpha-tocopherylacetate. After the feeding period, plasma retinol, alpha-tocopherol, cholesterol, HDL and triacylglyceride concentrations and aortic ring segment responses to KCl (70 mM), phenylephrine and acetylcholine (maximal tension, maximal relaxation and pD2 or -log ED50) were measured. The intake of vitamin-supplemented diets increased plasma alpha-tocopherol levels in rats fed hazelnut or fish oil, while retinol concentration was unaffected. Also, the vitamin supplement counteracted the specific hypercholesterolemic effect of hazelnut oil intake. The addition of a vitamin supplement augmented acetylcholine pD2 values in aortic ring segments of rats fed corn oil (p < 0.001), revealing that arteries were more prone to induced relaxation under this dietary condition. It also lowered the maximal ring tension in response to phenylephrine in rats fed hazelnut or olive oil. These results indicate that the intake of alpha-tocopherol and beta-carotene supplement can modulate the effect of dietary fat type on aortic ring segment responses to pharmacological agents in the rat.