PHYSIOLOGICAL CHARACTERISTICS OF HIGH-ALTITUDE ADAPTED ANIMALS

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The blue sheep as well as pika, and yak live in the Tibetan highlands to an altitude of 6,100 m and are typical animals adapted to high altitude among mammals of the world. These animals have a long history of habitation at high altitude and are considered to be "animals completely adapted to high altitude" because of their physiologic and morphological traits well-adapted to high-altitude environments. To evaluate physiologic characteristics of high-altitude adaptation of the blue sheep, changes in the pulmonary hemodynamics were examined in Qinghai Province, China (altitude 3,750 m). Primary items of measurement were the body weight (BW), systemic arterial pressure (Psa), pulmonary artery pressure (Ppa), hematocrit (Ht), left ventricular weight (LVW), right ventricular weight (RVW), and the blood gas profile. The principal finding of this study are: 1) Ht, at index of right ventricular hypertrophy (RVW/LVW), and oxygen consumption (VO2) were significantly smaller in the blue sheep compared with the pigs; 2) Ppa/Psa, an index of the right ventricular load, increased with the altitude in both species, but the increases were smaller in the blue sheep. From these observations, small Ht and RVW/LVW are considered to be characteristics of animals completely adapted to high altitude such as the pika.