Functional characterization and expression of endothelin receptors in rat carotid artery: involvement of nitric oxide, a vasodilator prostanoid and the opening of K⁺ channels in ET_B‐induced relaxation

Abstract

1 We aimed to functionally characterize endothelin (ET) receptors in the rat carotid artery. mRNA and protein expressions of both ET A and ET B receptors, evaluated by reverse transcriptionpolymerase chain reaction (RT-PCR) and Western immunoblotting, were detected in carotid segments. Immunohistochemical assays showed that ET B receptors are expressed in the endothelium and smooth muscle cells, while ET A receptors are expressed only in the smooth muscle cells. In endothelium-denuded vessels, levels of ET B receptor mRNA were reduced. 2 Vascular reactivity experiments, using standard muscle bath procedures, showed that ET-1 induces contraction in endothelium-intact and -denuded carotid rings in a concentration-dependent manner. Endothelial removal enhanced ET-1-induced contraction. BQ123 and BQ788, selective antagonists for ET A and ET B receptors, respectively, produced concentration-dependent rightward displacements of the ET-1 concentration-response curves. 3 IRL1620, a selective agonist for ET B receptors, induced a slight vasoconstriction that was abolished by BQ788, but not affected by BQ123. IRL1620-induced contraction was augmented after endothelium removal. 4 ET-1 concentration dependently relaxed phenylephrine-precontracted rings with intact endothelium. The relaxation was augmented in the presence of BQ123, reduced in the presence of BQ788 and completely abolished after endothelium removal. IRL1620 induced vasorelaxation that was abolished by BQ788 and endothelium removal, but not affected by BQ123. 5 Preincubation of intact rings with N G -nitro-L-arginine methyl ester (L-NAME), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), indomethacin or tetraethylammonium (TEA) reduced IRL1620-induced relaxation. The combination of L-NAME, indomethacin and TEA completely abolished IRL1620-induced relaxation while sulfaphenazole did not affect this response. 4-aminopyridine (4-AP), but not apamin, glibenclamide or charybdotoxin, reduced IRL1620-induced relaxation. 6 The major finding of this work is that it firstly demonstrated functionally the existence of both ET A and ET B vasoconstrictor receptors located on the smooth muscle of rat carotid arteries and endothelial ET B receptors that mediated vasorelaxation via NO-cGMP pathway, vasodilator cyclooxygenase product(s) and the activation of voltage-dependent K þ channels.

Adverse effects of pneumoperitoneum on renal function: involvement of the endothelin and nitric oxide systems

“…High abundance of ET A receptors has been detected in the aorta, heart, and kidney, whereas ET B receptors are expressed mainly in the endothelium and tubular epithelial cells of the collecting duct (24,25,26,40). Activation of ET A receptors on vascular smooth muscle cells (VSMC) increases intracellular Ca 2ϩ levels, leading to prolonged vasoconstriction and cell proliferation (31,35,41). In contrast, activation of ET B receptors, present on endothelial cells, induces the release of nitric oxide (NO) and prostaglandins, thus provoking transient vasodilation (41,43,44).…”

“…Activation of ET A receptors on vascular smooth muscle cells (VSMC) increases intracellular Ca 2ϩ levels, leading to prolonged vasoconstriction and cell proliferation (31,35,41). In contrast, activation of ET B receptors, present on endothelial cells, induces the release of nitric oxide (NO) and prostaglandins, thus provoking transient vasodilation (41,43,44). While it is accepted that ET A and ET B receptors mediate vasoconstriction and vasodilation, respectively, several studies have demonstrated that ET B receptors present on VSMC can elicit vasoconstriction (6 -8, 19 -21).…”

Aging and total stenosis triggers differential responses of carotid and basilar arteries to endothelin-1 and phenylephrine

“…The former is restricted to vascular smooth muscle and mediates vasoconstriction (Haynes et al 1993). Endothelial ETB receptors are describe to mediate relaxation via production of nitric oxide (NO) (Hirata et al 1993) and (or) prostacyclin (PGI2) (Filep et al 1991), while the ETB receptors located on vascular smooth muscle induces contraction (Ihara et al, 1992;Tirapelli et al, 2005). Endothelin-1-induced contraction of guinea-pig carotid is mediated by ETA receptors (Rubany et al 1994), which induces contraction, via influx of extracellular Ca 2+ (Rubany et al 1994).…”

Scleroderma Renal Crisis

“…It has three isoforms ET-1, ET-2 and ET-3. ET-1 binds to ET type A and ET type B receptors on muscular and endothelial cells (Tirapelli et al, 2005). It modulates vascular constriction and smooth muscle cell proliferation (Hirata, 1989;Takuwa, Takuwa, Yanagisawa, Yamashita, & Masaki, 1989).…”