Time-dependently enhanced pressor responses in rat lungs after chronic exposure to high altitude.

To investigate the de-acclimatization process with respect to pulmonary vasoreactivity after high-altitude exposure, we performed a study of changes in pressor responses over time in salt-perfused lungs from rats that had been exposed to high altitude (HA, n = 41, 20 weeks at actual 2400 m). Comparisons were made with the lungs of rats kept at low altitude (n = 8, kept at 610 m). We studied HA rats from the time just after removal from high altitude to 2 weeks after the exposure. The pressor responses of HA lungs to both 0.5 microgram-angiotensin II and 5 min airway hypoxia (3% O2) just after the exposure did not differ from those of controls, but their responses began to increase within 12 h, and reached a maximum 3 days after exposure ended. The increase was time-dependent. We conclude that pulmonary vasopressor responses are enhanced time-dependently during the very early stages of de-acclimatization after high-altitude exposure.