Advanced

Characterization of endothelium-dependent relaxation in guinea pig basilar artery - Effect of hypoxia and role of cytochrome P450 mono- oxygenase

Petersson, Jesper LU ; Zygmunt, Peter M. LU ; Jönsson, Peter LU and Högestätt, Edward D. LU (1998) In Journal of Vascular Research 35(4). p.285-294
Abstract

In the guinea pig basilar artery, acetylcholine and the calcium ionophore A23187 induced endothelium-dependent relaxations, which were not significantly affected by the nitric oxide (NO) synthase inhibitor N(ω)- nitro-L-arginine (L-NOARG; 0.3 mM) or the guanylate cyclase inhibitor ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one; 1-10 μM), or by these inhibitors combined. However, acetylcholine (10μM) and A23187 (3 μM) each significantly increased the tissue level of cGMP in the absence but not in the presence of L-NOARG, suggesting that NO is released from the vascular endothelium in this blood vessel. Treatment with the potassium (K) channel inhibitors charybdotoxin (0.1 μM) plus apamin (0.1 μM), a toxin mixture previously shown to... (More)

In the guinea pig basilar artery, acetylcholine and the calcium ionophore A23187 induced endothelium-dependent relaxations, which were not significantly affected by the nitric oxide (NO) synthase inhibitor N(ω)- nitro-L-arginine (L-NOARG; 0.3 mM) or the guanylate cyclase inhibitor ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one; 1-10 μM), or by these inhibitors combined. However, acetylcholine (10μM) and A23187 (3 μM) each significantly increased the tissue level of cGMP in the absence but not in the presence of L-NOARG, suggesting that NO is released from the vascular endothelium in this blood vessel. Treatment with the potassium (K) channel inhibitors charybdotoxin (0.1 μM) plus apamin (0.1 μM), a toxin mixture previously shown to inhibit relaxations mediated by endothelium-derived hyperpolarizing factor (EDHF) in this artery, had no effect on the A23187- induced relaxation but slightly inhibited the response to acetylcholine (E(max) was reduced by 24%). When the action of EDHF was prevented by these K channel inhibitors, the remaining relaxation was abolished by either ODQ (1 μM) or L-NOARG (0.3 mM), indicating that NO, apart from EDHF, contributes to the endothelium-dependent relaxations. Furthermore, ODQ (10 μM) abolished the relaxation induced by the NO donor S-nitroso-N-acetylpenicillamine. Thus, activation of soluble guanylate cyclase seems to be the only mechanism through which NO causes relaxation in this artery. When vessels were exposed to grave hypoxia (pO2 = 6 mm Hg), the NO-mediated relaxation (induced by acetylcholine in the presence of charybdotoxin plus apamin) disappeared. In contrast, EDHF-mediated responses (elicited by acetylcholine in the presence of L-NOARG) were only marginally affected by hypoxia (E(max) was reduced by 16%). 17-Octadecynoic acid (50 μM) and 5,8,11,14-eicosatetraynoic acid (10 μM), inhibitors ofcytochrome P450-dependent oxidation ofarachidonic acid, failed to inhibit the acetylcholine-induced relaxation in the presence of L- NOARG. The cytochrome P450-dependent arachidonic acid metabolite 11,12- epoxyecosatrienoic acid (0.3-3.0 μM) had no relaxant effect per se. In conclusion, EDHF and NO are both mediators of endothelium-dependent relaxations in the guinea pig basilar artery. However, during grave hypoxia, EDHF alone mediates acetylcholine-induced relaxation. The results further suggest that EDHF is not a metabolite of arachidonic acid formed by cytochrome P450 mono-oxygenase or generated by another oxygen-dependent enzyme in this artery.

(Less)
Please use this url to cite or link to this publication:
author
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Arachidonic acid, Cerebral arteries, Cyclic nucleotides, Cytochrome P, Hyperpolarization, Hypoxia, Membrane potential, Vascular endothelium
in
Journal of Vascular Research
volume
35
issue
4
pages
10 pages
publisher
Karger
external identifiers
  • scopus:0031821613
ISSN
1018-1172
DOI
10.1159/000025595
language
English
LU publication?
no
id
2d556d5e-af57-41ec-bbe3-bee6b0ba4bb0
date added to LUP
2019-05-31 21:37:46
date last changed
2019-07-09 04:47:26
@article{2d556d5e-af57-41ec-bbe3-bee6b0ba4bb0,
  abstract     = {<p>In the guinea pig basilar artery, acetylcholine and the calcium ionophore A23187 induced endothelium-dependent relaxations, which were not significantly affected by the nitric oxide (NO) synthase inhibitor N(ω)- nitro-L-arginine (L-NOARG; 0.3 mM) or the guanylate cyclase inhibitor ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one; 1-10 μM), or by these inhibitors combined. However, acetylcholine (10μM) and A23187 (3 μM) each significantly increased the tissue level of cGMP in the absence but not in the presence of L-NOARG, suggesting that NO is released from the vascular endothelium in this blood vessel. Treatment with the potassium (K) channel inhibitors charybdotoxin (0.1 μM) plus apamin (0.1 μM), a toxin mixture previously shown to inhibit relaxations mediated by endothelium-derived hyperpolarizing factor (EDHF) in this artery, had no effect on the A23187- induced relaxation but slightly inhibited the response to acetylcholine (E(max) was reduced by 24%). When the action of EDHF was prevented by these K channel inhibitors, the remaining relaxation was abolished by either ODQ (1 μM) or L-NOARG (0.3 mM), indicating that NO, apart from EDHF, contributes to the endothelium-dependent relaxations. Furthermore, ODQ (10 μM) abolished the relaxation induced by the NO donor S-nitroso-N-acetylpenicillamine. Thus, activation of soluble guanylate cyclase seems to be the only mechanism through which NO causes relaxation in this artery. When vessels were exposed to grave hypoxia (pO<sub>2</sub> = 6 mm Hg), the NO-mediated relaxation (induced by acetylcholine in the presence of charybdotoxin plus apamin) disappeared. In contrast, EDHF-mediated responses (elicited by acetylcholine in the presence of L-NOARG) were only marginally affected by hypoxia (E(max) was reduced by 16%). 17-Octadecynoic acid (50 μM) and 5,8,11,14-eicosatetraynoic acid (10 μM), inhibitors ofcytochrome P<sub>450</sub>-dependent oxidation ofarachidonic acid, failed to inhibit the acetylcholine-induced relaxation in the presence of L- NOARG. The cytochrome P<sub>450</sub>-dependent arachidonic acid metabolite 11,12- epoxyecosatrienoic acid (0.3-3.0 μM) had no relaxant effect per se. In conclusion, EDHF and NO are both mediators of endothelium-dependent relaxations in the guinea pig basilar artery. However, during grave hypoxia, EDHF alone mediates acetylcholine-induced relaxation. The results further suggest that EDHF is not a metabolite of arachidonic acid formed by cytochrome P<sub>450</sub> mono-oxygenase or generated by another oxygen-dependent enzyme in this artery.</p>},
  author       = {Petersson, Jesper and Zygmunt, Peter M. and Jönsson, Peter and Högestätt, Edward D.},
  issn         = {1018-1172},
  keyword      = {Arachidonic acid,Cerebral arteries,Cyclic nucleotides,Cytochrome P,Hyperpolarization,Hypoxia,Membrane potential,Vascular endothelium},
  language     = {eng},
  month        = {07},
  number       = {4},
  pages        = {285--294},
  publisher    = {Karger},
  series       = {Journal of Vascular Research},
  title        = {Characterization of endothelium-dependent relaxation in guinea pig basilar artery - Effect of hypoxia and role of cytochrome P<sub>450</sub> mono- oxygenase},
  url          = {http://dx.doi.org/10.1159/000025595},
  volume       = {35},
  year         = {1998},
}