We studied the effect of Angiotensin II (Ag II) and of an AT1 receptor blocker on the isolated mesenterial artery of Wistar rats, in two experimental conditions : on tissues with intact endothelium and with denuded endothelium. Ag II, one of the strongest vasoconstrictor substances, used in different concentrations, caused contractions in a concentrationdependent manner. Losartan administrated before or after Ag II, in both cases significantly reduced the contractions caused by Ag II. The effects of both agents were influenced by the endotelium: contraction was increased by its presence, relaxation was promoted by its absence.
Keywords: Wistar rats, endothelium, mesenteric artery, losartan, angiotensin II.