TIME COURSE OF VASCULAR REACTIVITY TO CONTRACTING AND RELAXING AGENTS AFTER ENDOTHELIAL DENUDATION BY BALLOON ANGIOPLASTY IN RAT CAROTID ARTERY

Endothelial injuries induced by different stimuli lead to proliferation of intimal vascular smooth muscle cells with formation of neointima. In this functional study, we evaluated the reactivity to contracting and vasorelaxing agents in Wistar rat carotid artery at different times (1, 7, 14, 21 and 28 days) after endothelial denudation with angioplastic balloon technique. Injured (IC) and uninjured carotid artery rings (UC) were placed in an isolated organ bath for isometric force displacement. IC collected at 1, 7, 14, 21 and 28 days showed a reduction in contraction to phenylephrine (0.3M), angiotensin II (0.1M), U46619 (0.1M), KCl (60 mM) and A23187 (1M) at any experimental time compared to rings obtained from UC. The evaluation of endothelial-derived relaxing or hyperpolarizing factor (EDRF or EDHF), induced by acetylcholine (0.001–1M) in presence of indomethacin (10M) or indomethacin and N-nitro-l-arginine methyl ester hydrochloride (l-NAME) (10 and 100M, respectively), was carried out at 14, 21 and 28 days. The EDRF-induced relaxation was significantly (P < 0.0001) reduced at 14 days and it improved through out the observation time, indeed at 28 days it was indistinguishable from UC relaxation curve. In contrast, the EDHF-induced relaxation was significantly (P < 0.0001) reduced at all experimental time. A significant reduction in nitric oxide-induced relaxation, sodium nitroprusside (0.001–10M), was observed at 7, 14 and 21 days, but not at 28 days. The relaxation induced by diazoxide (3–300M), an opener of KATP channels, was significantly reduced only at 7 days but not at 14, 21 and 28 days. Western blot analysis of myosin heavy chain revealed that up to 28 days the re-differentiation (maturity state) of smooth muscle cells was not yet reached. In conclusion, our data showed that hyporeactivity to contracting and relaxing agents in endothelial denuded carotid of rats could be linked to a multifactorial condition in which reduction of receptors and alterations in post-receptor transductions in neointima may produce modification of protein expression and/or variation in ion flux where calcium could have a pivotal rol