Journal
JOURNAL OF APPLIED PHYSIOLOGY
Volume 98, Issue 5, Pages 1691-1696Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/japplphysiol.01146.2004
Keywords
hypoxia-reoxygenation; vascular reactivity; experimental model; obstructive sleep apnea; ischemia-reperfusion
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Coronary heart disease is frequently associated with obstructive sleep apnea syndrome and treating obstructive sleep apnea appears to significantly improve the outcome in coronary heart disease. Thus we have developed a rat model of chronic intermittent hypoxia (IH) to study the influence of this condition on myocardial ischemia-reperfusion tolerance and on functional vascular reactivity. Wistar male rats were divided in three experimental groups ( n = 12 each) subjected to chronic IH ( IH group), normoxia (N group), or control conditions ( control group). IH consisted of repetitive cycles of 1 min ( 40 s with inspired O-2 fraction 5% followed by 20 s normoxia) and was applied for 8 h during daytime, for 35 days. Normoxic cycles were applied in the same conditions, inspired O2 fraction remaining constant at 21%. On day 36, mean arterial blood pressure ( MABP) was measured before isolated hearts were submitted to an ischemia-reperfusion protocol. The thoracic aorta and left carotid artery were also excised for functional reactivity studies. MABP was not significantly different between the three experimental groups. Infarct sizes ( in percent of ventricles) were significantly higher in IH group (46.9 +/- 3.6%) compared with N (26.1 +/- 2.8%) and control (21.7 +/- 2.1%) groups. Vascular smooth muscle function was similar in aorta and carotid arteries from all groups. The endothelium-dependent relaxation in response to acetylcholine was also similar in aorta and carotid arteries from all groups. Chronic IH increased heart sensitivity to infarction, independently of a significant increase in MABP, and did not affect vascular reactivity of aorta and carotid arteries.
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