ABSTRACT
We examined effects of a 2-week infusion of angiotensin II (AII, 250 ng x kg[-1] x min[-1]) on properties of mesenteric resistance arteries (MrA) and superior epigastric arteries (SEA) of male Wistar rats. Histochemistry and pharmacological tools showed that MrA are densely innervated, whereas SEA are only sparsely innervated. AII infusion resulted in a significant elevation in mean arterial pressure and in plasma AII and noradrenaline levels. Organ chamber studies and morphometry were used to determine arterial contractile reactivity and structure. After AII infusion, in MrA (i) maximal contractile responses to 125 mM K+, noradrenaline, serotonin and adrenergic nerve stimulation were significantly increased, without modification of the sensitivity to these stimuli and (ii) a significant increase in media cross-sectional area and media thickness was observed without alterations in lumen diameter. The observed increase in vascular reactivity could fully be attributed to the observed increase in wall mass since no alterations in maximal active wall stress were noted. In SEA, no significant changes in responsiveness to vasoconstrictor stimuli or in wall structure were observed. These findings suggest that perivascular nerves are involved in the hypertrophy and subsequent hyperreactivity of small arteries in rats exposed for 2 weeks to a low dose of AII.
