Regional differences in endothelium‐dependent relaxation in the rat: contribution of nitric oxide and nitric oxide‐independent mechanisms

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Abstract

Relaxant effects of acetylcholine (ACh), histamine, calcitonin gene‐related peptide (CGRP) and the calcium ionophore A23187 were examined in rat femoral (Ø ≅ 0.2 mm), mesenteric (0.2 mm), intrarenal (0.2 mm) and hepatic (0.3 mm) arteries, and aorta (2 mm). Acetylcholine elicited an endothelium‐dependent relaxation in all arteries. Histamine induced an endothelium‐dependent relaxation in aorta, and mesenteric and intrarenal arteries, whereas a partly endothelium‐dependent and mainly endothelium‐independent relaxation was observed in hepatic and femoral arteries, respectively. In hepatic, mesenteric and intrarenal arteries, CGRP induced an endothelium‐independent relaxation, whereas either small or no relaxation was obtained in aorta and femoral arteries respectively. A23187 induced an endothelium‐dependent relaxation in the aorta and hepatic artery, whereas A23187 had no relaxant effect in femoral, mesenteric and intrarenal arteries. Nω‐nitro‐l‐arginine (l‐NOARG, 0.3 mM) reduced the maximum ACh‐induced relaxation (in the presence of 10 μM indomethacin) by 66% in the aorta, and abolished the relaxation in femoral and intrarenal arteries. A marked l‐NOARG/indomethacin‐resistant relaxation was obtained in mesenteric and hepatic arteries. Levcromakalim induced a concentration‐dependent and almost complete relaxation in all arteries. When contracted by a 60 mM K+ solution, all arteries responded to ACh with a relaxation that was abolished by l‐NOARG. These results demonstrate marked regional differences with regard to the vascular effects of ACh, histamine, CGRP and A23187. Whereas nitric oxide appears to mediate endothelium‐ dependent relaxation regardless of the vascular region, an l‐NOARG/indomethacin‐resistant relaxation, presumably mediated by an endothelium‐derived hyperpolarizing factor, was observed only in mesenteric and hepatic arteries, and aorta.

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Subject classification (UKÄ) – MANDATORY

  • Pharmacology and Toxicology

Keywords

  • arteries, hyperpolarization, membrane potential, nitric, vascular endothelium
Original languageEnglish
Pages (from-to)257-266
Number of pages10
JournalActa Physiologica Scandinavica
Volume155
Issue number3
Publication statusPublished - 1995 Jan 1
Publication categoryResearch
Peer-reviewedYes