Effect of hexasulfobutylated C₆₀ on the isolated aortic ring of guinea pig

The effects of hexasulfobutylated C₆₀ (FC₄S) and monomalonic acid C₆₀ (MMA C₆₀), the fullerene C₆₀ derivatives, on isolated endothelium-containing or endothelium-denuded aorta of guinea pig were studied pharmacologically in vitro. In the endothelium-containing preparation of the aortic rings, phenylephrine (PHE) elicited contracture and acetylcholine (ACh) elicited a relaxing effect on the PHE-precontracted preparation. In the PHE-precontracted preparation, MMA C₆₀ (10 μmol/l) did not elicit a relaxing effect on the PHE-precontracted preparation. However, MMA C₆₀ (10 μmol/l) significantly reduced the maximum response of the relaxation elicited by ACh. FC₄S itself significantly relaxed the PHE-precontracted aortic rings. ACh-induced relaxation in PHE-precontracted endothelium-containing strips of the aortic rings was significantly potentiated if pretreated with FC₄S (10 μmol/l). In the denuded aortic rings, FC₄S did not elicit the relaxing effect in the PHE-precontracted preparation. The relaxing effect of FC₄S on the PHE-precontracted preparation was not altered when superoxide dismutase (250 units/ml) was pretreated. However, the relaxing effect was reduced when N(G)-nitro-L-arginine methyl ester (L-NAME, 1 mmol/l) or methylene blue (1 μmol/l) was pretreated. These results demonstrated that the vasorelaxation effect of FC₄S on the PHE-precontracted aortic ring is partly dependent on the release of nitric oxide (NO) or an NO-derived substance from the vascular endothelium.