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KMID : 0383119680160010021
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Journal of Aerospace Medicine
1968 Volume.16 No. 1 p.21 ~ p.29
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EFFECT OF CHRONIC HYPOXIA ON CIRCULATORY SYSTEM IN RABBITS
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Abstract
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It has been long recognized that there is a tendency toward bradycardia and hypotension in the natives living at high altitude after a degree of acclimatization has been reached (Monge et al., 1931; Rotta, 1947). Recently Kim and Choo (1966) reported that blood pressures of pilots were slightly lower than those of normal Koreans in both systolic and diastolic pressures. This indicates that there may be a interrelationship between chronic or intermittent hypoxia and circulatory function.. This experimental study was undertaken to reevaluate the effect of chronic hypoxia to circulatory system of rabbits.
The. experiments were conducted on adult albino rabbits of both sexes, weighing .approximately 2 kg.and divided into 3 groups, the chronic .hypoxia, recovery aM control group. 1) Chronic hypoxic group: The rabbits were exposed 8 hours a day and 5 days a week to a simulated altitude of 18,000-25, 000 feet for a period of 10 weeks. 2) Recovery group: The rabbits after 10 days from the exposure to the chronic hypoxia. 3) Control group The normal rabbits without the exposure to the chronic .hypoxia. The anirnals were sacrificed by air embolism and then blood sample was obtained by a aspiration from the inferior vena cava to determine RBC and hemoglobin, values. The isolated atria and aortic strips were prepared. according to procedure. described by Lee and Shideman (1959) and Furchgott (1960) respectively and their responses to norepinephrine were obtained. The myocardial concentration of catecholamines were determined spectrophoto-fluorometrically by the method of Shore and Olin (1958),
Following results were obtained.
1. The RBC count and hemoglobin value increased due to the exposure of chronic hypoxia. But these changes decreased and returned to normal progressively without a constant exposure in hypoxic environment even after the chronic hypoxia.
2. It appeared a tendency to decrease the myocardial content of catecholamines after chronic hypoxia, but there was no significant difference between chronic hypoxia and control group.
3. The cardio stimulant action of norepinephrine in the isolated atria and the vasoconstictor activity of norepinephrine in the isolated aortic atrips significantly decreased in chronic hypoxic rabbits compared to normal rabbits.
From the above results, it may be concluded that the sensitivity of circulatory system (heart and artery) to catecholamine markedly decreased due to the exposure of chronic hypoxia.
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