ALTERED ACTIVE BUT NOT PASSIVE PROPERTIES OF MESENTERIC RESISTANCE ARTERIES FROM THE VITAMIN-E-DEPRIVED RAT

1 We tested the hypothesis that lowering antioxidant protection throug h dietary vitamin E deprivation would alter active and passive mechani cal properties in resistance arteries of the rat. Specifically, we hyp othesized that vascular tone in isolated mesenteric arteries of the vi tamin E-deprived rats would be altered due to impaired endothelial inf luences of nitric oxide and/or prostaglandins. 2 Lumen diameter and wa ll thickness were measured in pressurized arteries (approximate to 250 mu m diameter) from control (n=9) and vitamin E deprived (n=9) Spragu e-Dawley female rats by use of a dimension analysing system. 3 Treatme nt with a cyclo-oxygenase inhibitor (meclofenamate) did not affect the basal vascular tone in either group. Treatment with a nitric oxide sy nthase inhibitor (N-G-methyl-L-arginine) caused a significant increase in basal tone only in the vitamin E-deprived rats (% tone: 6.2+/-1.1 vs 1.2+/-0.3%; P<0.05). When tone was induced to 25% of the initial di ameter with phenylephrine, treatment with the nitric oxide synthase in hibitor resulted in a greater potentiated tone in the vitamin E-depriv ed rats compared to the controls (26.5+/-2.7 vs 16.4+/-3.4%; P<0.05); suggesting a greater nitric oxide affect in the vessels from the vitam in E-deprived rats. Meclofenamate treatment in the induced tone arteri es significantly relaxed (-17.4+/-4.0%; P<0.05) only the arteries from the vitamin E-deprived rats, indicating that a vasoconstrictor was mo difying tone. The passive characteristics of distensibility and stress -strain relationship were not different between the two groups of rats . 4 In summary, vitamin E deprivation in the rat enhanced the modulati on of vascular tone by both the nitric oxide and cyclo-oxygenase pathw ays but did not alter passive characteristics of mesenteric arteries.