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Cardiac Outcomes of Sleep Apnea Studied in Rats

Endothelin system plays a major role in rat model of condition

THURSDAY, April 9 (HealthDay News) -- The endothelin system, a potent vasoconstrictor and promoter of vascular growth, plays a major role in the cardiovascular consequences of obstructive sleep apnea in a rat model of the condition, researchers report in the April 14 issue of the Journal of the American College of Cardiology.

Elise Belaidi, Ph.D., from INSERM in Grenoble, France, and colleagues induced chronic intermittent hypoxia, a major component of obstructive sleep apnea, in normal rats and in rats genetically prone to develop hypertension, to examine the role of the endothelin system in the cardiovascular consequences of hypoxia.

The researchers found that chronic hypoxia increased hypertension and infarct size in the genetically hypertensive rats, which was accompanied by changes in the levels of several components of the endothelin system. The activity of myocardial hypoxia-inducible factor (HIF)-1 also increased and was linked to the endothelin system only after inducing hypoxia. Treatment with bosentan, which blocks the endothelin system, during chronic hypoxia prevented hypertension and the increase in infarct size, the authors report.

"In spontaneous hypertensive rats, activation of the endothelin system, mediated by HIF-1 activity, is responsible for the enhanced susceptibility to chronic intermittent hypoxia and for its associated cardiovascular consequences leading to hypertension and ischemic injury," Belaidi and colleagues conclude. "Furthermore, the beneficial effects of bosentan suggest exploring endothelin antagonists as possible therapeutic tools in obstructive sleep apnea."

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