Inhibitory effect of a fullerene derivative, monomalonic acid C₆₀, on nitric oxide-dependent relaxation of aortic smooth muscle

1. Effects of a fullerene C₆₀, derivative, monomalonic acid C₆₀ (MMA C₆₀), on endothelium-containing or denuded aorta of rabbit, trachea and ileum of guinea pig, and stomach (fundus), vas deferens and uterus of rat were studied pharmacologically. 2. MMA C₆₀ (10^-5 M) significantly reduced the maximum response of the relaxation induced by acetylcholine in endothelium containing thoracic aorta of rabbit, and the acetylcholine induced relaxation was recovered in the presence of superoxide dismutase (SOD, 250 units/ml). 3. Nitric oxide-generating agent, S-nitroso-N-acetylpenicillamine, caused the relaxation of aorta without endothelium in a concentration dependent manner, and the concentration-response curve was shifted to the right in the presence of MMA C₆₀. This inhibitory effect of the derivative was also masked in the presence of superoxide dismutase (SOD). 4. Sodium nitroprusside-induced relaxation was not affected by either MMA C₆₀ Or SOD. In the other tissues, this C₆₀ derivative had no effect on the responses induced by any agonist. 5. These observations indicate that MMA C₆₀ inhibits the endothelium dependent relaxation induced by acetylcholine but does not affect the agonist-induced contractile response of smooth muscle.