Abstract
Summary
The superovulation and embryo transplantation techniques were used to obtain four sibling calves from four different mother cows. The semen and ova were obtained from one bull and one cow, respectively, known to have susceptible pulmonary hypertension when exposed to low-pressure environments. The recipient mothers were healthy ordinary cows purchased at high terrestrial elevations, thus, supposed to be resistant to high-altitude-induced pulmonary hypertension. Both cows and calves, 5 month of age, were tested for pulmonary hypertension in a hypobaric chamber at 4500 m simulated altitude (P B = 430 torr) for 2 hr. The increase in pulmonary arterial pressure at high altitude in the calves (40 ± 5 torr) was much greater than that in the cows (10 ± 3 torr), demonstrating that they were susceptible and resistant cattle, respectively, to high-altitude-induced pulmonary hypertension. Therefore, susceptible calves were obtained from resistant cows. This study supports the hypothesis that pulmonary vascular hyperreactivity to hypoxia is genetically transmitted.
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