EFFECT OF N-ACETYLCYSTEINE ON VASCULAR ENDOTHELIUM FUNCTION IN AORTA FROM OOPHORECTOMIZED RATS

1. Experiments were performed to examine and to compare vascular endot helial function in aortic rings from oophorectomized and from ovary-in tact rats and to test the effect of thiol compound as N-acetylcysteine on endothelial function. 2. In precontracted aortic rings from oophor ectomized and intact rats, vascular endothelial function was evaluated by measuring changes in isometric force in response to cumulative dos es of superoxide dismutase, acetylcholine and sodium nitroprusside. 3. In studies designed to assess the tone-related release of nitric oxid e from aortic rings moderately precontracted with phenylephrine, super oxide dismutase produced a lower concentration-related relaxant respon se in aortic rings from oophorectomized rats than from ovary intact ra ts. 4. Acetylcholine caused a concentration- and endothelium-dependent relaxation of less magnitude in aortic rings from oophorectomized ani mals compared with those from ovary-intact rats. Addition of N-omega-n itro-L-arginine methyl ester eliminated the relaxation induced by both superoxide dismutase and acetylcholine. 5. No differences between gro ups were noticed in the concentration-relaxation curve induced by sodi um nitroprusside. 6. Preincubation with N-acetylcysteine normalized th e depressed vasorelaxant response to acetylcholine in the aortic rings from oophorectomized rats, whereas the concentration-response curve f or acetylcholine in aortic rings from ovary-intact rats did not alter. 7. These results suggest that the absence of ovary estrogens is assoc iated with a vascular endothelium dysfunction that can be reverted by addition of N-acetylcysteine, a thiol-containing compound with a free radical scavenger effect. (C) 1998 Elsevier Science Inc.