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.