Angiotensin II Induces Media Hypertrophy and Hyperreactivity in Mesenteric but Not Epigastric Small Arteries of the Rat

Abstract

We examined effects of a 2-week infusion of angiotensin II (All, 250 ng· kg^-1•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. All infusion resulted in a significant elevation in mean arterial pressure and in plasma All and noradrenaline levels. Organ chamber studies and morphometry were used to determine arterial contractile reactivity and structure. After All 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

Contractile and relaxing reactivity in carotid and femoral arteries of chicken embryos

“…In the present study we analyzed isolated arteries of the chicken embryo. The use of in vitro approaches, which are well established for adult arteries (e.g., 7,8,29), allow quantification of responses and sensitivities of individual blood vessels to various vasoactive agents and allow us to quantify neurogenic and endothelium-dependent responses in the absence of modulatory circulating hormones. We compared femoral and carotid arteries as model systems for a peripheral and a central vascular bed.…”

“…It may furthermore be more prominent in vascular smooth muscle cells of mesodermal origin than in those that are derived from the neural crest and which primarily populate the blood vessels in the cranial region. In addition to altering the pharmacological properties of the innervated blood vessel (e.g., see 29), the perivascular sympathetic innervation can initially stimulate growth and proliferation of the smooth muscle cells and subsequently promote the development and maintenance of a contractile phenotype (for review, see Ref. 6).…”

“…Each artery was stretched to its individual optimal lumen diameter, i.e., the diameter at which it developed the strongest contractile response to 125 mM K ϩ -KRB (K-KRB), using a diameter-tension protocol as previously described for mammalian small arteries (Ref. 29; Fig. 1).…”

“…To demonstrate the presence of l-norepinephrine (NE)-containing nerves, we stained whole mount vessel preparations with glyoxylic acid (24,29). Vessel segments were opened longitudinally and were incubated for 30 min at 20°C in 2% glyoxylic acid in 10% sucrose containing phosphate buffer (pH 7.2).…”

Acetylcholine produces contractions mediated by the cyclooxygenase pathway in arterial vessels in the Chilean frog (Calyptocephalella gayi)

“…Each vessel segment was stretched to its optimal diameter, i.e. the diameter at which it developed a contraction response to PSS-K + , (PSS-K + solution, NaCl was replaced by an equimolar amount of KCl) using a diameter-tension protocol as previously described for mammalian small arteries (Stassen et al, 1997). In this way, the myograph permitted direct measurement of vessel wall tension while the internal diameter was controlled.…”