Effect of age on noradrenaline responses in rat tail artery and aorta: role of endothelium.

1. We have analysed the impact of ageing on the contractile responses induced by noradrenaline on endothelium intact and denuded aorta and tail artery rings from Sprague-Dawley rats. In addition, the influence of age on noradrenaline stimulation of phosphoinositide hydrolysis was investigated. 2. The sensitivity and the phosphatidylinositol hydrolysis to noradrenaline in aorta and tail artery were not modified by age. Intact tail artery rings showed a greater maximal contraction (Emax) to noradrenaline in old as compared to young animals. However, no Emax modification by age was observed in aorta (intact or denuded) and in denuded tail artery rings. 3. Removal of endothelial cells resulted in an increase of noradrenaline sensitivity but not the Emax in aorta from each age group. 4. In contrast, the absence of endothelium did not modify (young rats) or diminish (aged rats) the alpha 1-adrenoceptor-mediated responses in tail artery. 5. These results seem to indicate that: (1) there is no influence of age on noradrenaline responses in presence of endothelium; and (2) responses in denuded preparations seem to indicate a differential role of endothelium on noradrenaline responses obtained in different vascular beds.