Intermittent hypoxia in rats increases myogenic tone through loss of hydrogen sulfide activation of large-conductance Ca(2+)-activated potassium channels.
Circ Res
; 108(12): 1439-47, 2011 Jun 10.
Article
em En
| MEDLINE
| ID: mdl-21512160
ABSTRACT
RATIONALE Myogenic tone, an important regulator of vascular resistance, is dependent on vascular smooth muscle (VSM) depolarization, can be modulated by endothelial factors, and is increased in several models of hypertension. Intermittent hypoxia (IH) elevates blood pressure and causes endothelial dysfunction. Hydrogen sulfide (H(2)S), a recently described endothelium-derived vasodilator, is produced by the enzyme cystathionine γ-lyase (CSE) and acts by hyperpolarizing VSM. OBJECTIVE:
Determine whether IH decreases endothelial H(2)S production to increase myogenic tone in small mesenteric arteries. METHODS ANDRESULTS:
Myogenic tone was greater in mesenteric arteries from IH than sham control rat arteries, and VSM membrane potential was depolarized in IH in comparison with sham arteries. Endothelium inactivation or scavenging of H(2)S enhanced myogenic tone in sham arteries to the level of IH. Inhibiting CSE also enhanced myogenic tone and depolarized VSM in sham but not IH arteries. Similar results were seen in cerebral arteries. Exogenous H(2)S dilated and hyperpolarized sham and IH arteries, and this dilation was blocked by iberiotoxin, paxilline, and KCl preconstriction but not glibenclamide or 3-isobutyl-1-methylxanthine. Iberiotoxin enhanced myogenic tone in both groups but more in sham than IH. CSE immunofluorescence was less in the endothelium of IH than in sham mesenteric arteries. Endogenouse H(2)S dilation was reduced in IH arteries.CONCLUSIONS:
IH appears to decrease endothelial CSE expression to reduce H(2)S production, depolarize VSM, and enhance myogenic tone. H(2)S dilatation and hyperpolarization of VSM in small mesenteric arteries requires BK(Ca) channels.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Vasodilatação
/
Endotélio Vascular
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Poluentes Atmosféricos
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Canais de Potássio Ativados por Cálcio de Condutância Alta
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Sulfeto de Hidrogênio
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Hipóxia
/
Artérias Mesentéricas
Tipo de estudo:
Prognostic_studies
Limite:
Animals
Idioma:
En
Revista:
Circ Res
Ano de publicação:
2011
Tipo de documento:
Article
País de afiliação:
Estados Unidos