Influence of Hypoxia on Endothelium-Derived NO-Mediated Relaxation in Rat Carotid, Mesenteric and Iliac Arteries

Abstract

Individual vascular beds exhibit differences in vascular reactivity. The present study examined the influence of hypoxia on endothelium-dependent, especially nitric oxide (NO)-mediated, relaxation in the isolated rat common carotid, superior mesenteric and external iliac arteries. Hypoxia for 1 and 3 h had no effects on the relaxations caused by acetylcholine (ACh) and sodium nitroprusside (SNP) in common carotid and external iliac arteries. In addition, NO synthase inhibitor N^G-nitro-<smlcap>L</smlcap>-arginine (<smlcap>L</smlcap>-NA, 10 μmol/l)-resistant, endothelium-dependent relaxations by ACh were also unaffected by hypoxia in these arteries. On the other hand, ACh-induced relaxation in superior mesenteric arteries was significantly impaired by exposure to hypoxia, while this condition did not affect the relaxation induced by SNP or ACh in the presence of <smlcap>L</smlcap>-NA. This impairment was partially prevented by treatment with tempol (3 mmol/l), a superoxide scavenger. These findings demonstrate a marked heterogeneity in response to hypoxia in rat arteries. Briefly, acute hypoxia induces impairment of endothelium-derived NO-mediated relaxation through the decrease in its bioavailability in the superior mesenteric, but not in common carotid or external iliac, arteries. Furthermore, superoxide seems to be one causal factor responsible for the undesirable effect of hypoxia.

Role of gap junctions in the contractile response to agonists in the mesenteric resistance artery of rats with acute hypoxia

“…Hypoxia vascular model. An acute hypoxia model of MRA segments in vitro was established according to previous studies (4,19,20). The rats were euthanized and the descending third-order branch of the MRA (~10 mg) was removed.…”

“…An adequate O 2 supply via the vasculature is important for the normal function of the cardiovascular system (1). Reduced or impaired blood flow patterns in the larger conductance and resistance arteries are a factor in numerous pathological conditions that are associated with hypoxia-induced injury (2)(3)(4). It is known that acute hypoxia is associated with a number of cardiovascular diseases, including myocardial infarction (5), pulmonary hypertension (6,7) and mesenteric ischemia (8) and thus leads to an increase in blood pressure together with peripheral vascular resistance due to reduction of tone in certain vascular beds and critical injury or death (4).…”