Chronic exercise does not prevent hypoxia-induced increased aortic sensitivity to endothelin in rats

Area of Science:

• Cardiovascular Physiology
• Exercise Science
• Environmental Physiology

Background:

• Prolonged exposure to hypoxia can alter vascular reactivity.
• Endothelin-1 (ET-1) is a potent vasoconstrictor involved in vascular tone regulation.
• The impact of exercise on ET-1 reactivity under hypoxic conditions is not fully understood.

Purpose of the Study:

• To investigate the effect of regular exercise on vascular reactivity to ET-1 following prolonged hypoxic stress.
• To determine if exercise can mitigate hypoxia-induced changes in ET-1 sensitivity.

Main Methods:

• Male Dark Agouti rats were divided into normoxic sedentary, normoxic exercised, chronic hypoxic sedentary, and chronic hypoxic exercised groups.
• Vascular reactivity to ET-1 was assessed in isolated rat thoracic aorta preparations.
• Experiments were conducted with and without endothelium, and with the ET-1 receptor antagonist bosentan.

Main Results:

• Chronic hypoxia significantly increased aortic sensitivity to ET-1.
• Exercise training reduced ET-1 sensitivity in normoxic rats but had no effect in hypoxic rats.
• Endothelium removal increased ET-1 sensitivity in normoxic exercised rats, suggesting a role for endothelial function.

Conclusions:

• Exercise may partially improve vascular function through enhanced endothelial function related to ET-1 reactivity.
• Chronic exercise training does not appear to counteract the increased vasoconstriction to ET-1 induced by chronic hypoxia.