The upregulation of angiotensin-converting enzyme during neointima formation does not have functional consequences

The aim of this study was to analyze if the upregulation of angiotensin-con verting enzyme and AT(1) receptors observed in a model of neointima formati on results in increased contractions to angiotensin I (AI) and AII. Endothe lial denudation was performed in left common carotid arteries of 3-month-ol d male Sprague-Dawley rats. Rats were killed at days 0, 4, 8 and 14 after i njury and vascular reactivity was assessed in an organ bath. Responses were always compared with their contralateral vessels as a control. Contractile responses to 75 mM KCl were similar between groups. Noradrenaline (0.1 muM ) induced significantly higher contractions at days 0 and 4. Relaxation to acetylcholine (Ach) (1 nM to 0.1 mM) was suppressed at day 0 and increased with time after injury. Relaxations to sodium nitroprusside (0.1 nM to 0.1 mM) were similar at all time points studied. Responses to AI and AII were i ncreased at early steps of neointima formation and decreased with time afte r injury correlating with increased responses to Ach. Concentration-respons e curves to AI and AII had similar EC50 or E-max values at the same time po ints. These results indicate that in the rat i) neointima formation does no t impair contractile responses to KCl nor relaxation to SNP, ii) a funtiona l endothelium seems to regenerate with time after injury, and iii) the incr ease in ACE activity and AT1 receptor number does not have functional conse quences. (C) 2001 Elsevier Science Inc. All rights reserved.