[The effect of acute pulmonary alveolar hypoxia on canine plasma endothelin-1 levels].

The effect of acute pulmonary alveolar hypoxia on plasma endothelin (ET)-1 levels was observed in 10 anesthetized dogs (hypoxic group). Plasma ET-1 like immunoreactivity (-LI) levels increased significantly at the fifth, fifteenth, sixtieth minute after hypoxia (fractional inspiratory O2 concentration 10%), but they had no remarkable change at the thirtieth minute. It was suggested that the first peak of ET-1-LI levels (the fifth minute) might be caused by the release of endothelin-1 which was formed before hypoxia and the second peak could be associated with the secretion of ET-1 after hypoxia. The effect of ligustrazine on plasma ET-1-LI levels during hypoxia was also investigated in other 8 anesthetized dogs. Plasma ET-1-LI levels reduced significantly at the fifth minute after the injection of ligustrazine, compared with the hypoxic group. The result demonstrated that ligustrazine can inhibit the release of ET-1, which could be correlated with the blockade of calcium channel caused by ligustrazine.