Free radical production in aortic rings from rats fed a fish oil-rich diet

To study the effect of the degree of unsaturation of dietary fatty acids on the production of free radicals and on the vascular smooth muscle tone in rings of the aorta, Sprague-Dawley rats were fed a semipurified diet contai ning 5% lipids from either corn oil (CO) or menhaden oil (MO) for 8 wk. The MO diet did not change the basal or NADPH-dependent superoxide anion (O-2( -).) release. There were no significant differences in phenylephrine-induce d contractions between the two groups in intact rings. However, these contr actions increased in endothelium-intact aortic rings from the MO group afte r addition of the nitric oxide (. NO) synthase inhibitor N-G-nitro-L-argini ne and in endothelium-denuded rings, both indicating a greater endothelial basal . NO production in rats fed with the MO diet. Endothelium-dependent r elaxations in response to acetylcholine were more prominent in rings from t he MO group. These differences were not due to an increased smooth muscle r esponse to . NO, because relaxations were the same using an exogenous . NO donor. Our results indicate that dietary MO did not modify O-2(-). release by the vessel wall or relaxation due to the cyclooxygenase pathway, but it potentiated endothelial production of . NO.