Effect of removal of adventitia on vascular smooth muscle contraction and relaxation

The aim of the present study was to determine whether the adventitia of lar ge arteries modulates vascular function. We developed a method to obtain fu nctional vascular rings devoid of adventitia. Carotid and iliac arteries fr om 3-mo-old Sprague-Dawley rats were denuded from adventitia after treatmen t with collagenase followed by gentle peeling. Adventitia removal and integ rity of the media was demonstrated by optical and confocal microscopy. Arte rial rings with or without adventitia and with or without endothelium were mounted in an organ bath for isometric tension recording. Responses to 75 m M KCl or norepinephrine (0.1 nM-1 muM) were significantly reduced in segmen ts without adventitia. Acetylcholine-induced relaxation (0.1 muM-0.1 mM) wa s enhanced in arteries without adventitia, whereas sodium nitroprusside-ind uced responses were not modified. These results demonstrate that the combin ation of stripping with a previous collagenase treatment allows us to obtai n functional rings devoid of adventitia and that this layer plays a role in contractile capacity and in endothelium-modulated responses.