Alteration in hypoxic pulmonary vasoconstriction during hypothermia in dogs

Summary

This study was performed to investigate the pulmonary vascular reactivity during hypothermia. It was found that the pulmonary vessels were more sensitive to alveolar hypoxia in hypothermic dogs, and that hypoxic pulmonary vasoconstriction (HPV) was enhanced, which could be inhibited by α₁-adrenoceptor blocker prazosin. The concentration of arterial plasma norepinephrine (NE) increased in dogs with hypothermia or in those with hypothermia plus hypoxia, but there was no significant difference between these two groups. The plasma level of 5-hydroxytryptamine (5-HT) Was reduced during hypoxia in hypothermie dogs. Increase in plasma 6-keto-PGF₁α, which appeared in hypoxic dogs, was not observed during hypoxia in hypothermie dogs. These findings suggest that a potentiation in the sensitivity and reactivity of α-adrenoceptor in pulmonary vessels and a decrease in the modulation of PGI₂ might be responsible for the enhancement of HPV. 5-HT seemed not to play a contributing role in the alteration of HPV.