Response of the left ventricular connective tissue to hypoxia

The collagen content (measured as myocardial concentration of hydroxyproline) and dry weight (expressed as ventricle weight to body weight ratio) were determined in the left ventricle of male Sprague-Dawley rats (200--220 g b.wt.) exposed to a simulated altitude of 7,000 m for 18 h a day for 10 days in a hypobaric chamber. Hypoxia resulted in a significant increase (P less than 0.001) in the mass of the left ventricle with a concomitant significantly increased collagen concentration (P less than 0.001). The data indicate that hypoxia effects the synthesis of a significant amount of connective tissue in the left ventricle, which is the ventricle not exposed to pressure load. These results may be related to clinical, hemodynamic, and pathologic observations showing the left ventricular dysfunction in patients with chronic respiratory insufficiency. Since the amount of collagen in the left ventricle might interfere with contractile function, it is suggested that the hypoxia in these patients could affect the left ventricular myocardium via a direct action on the connective metabolism.