Decrease in immunoreactivity and vasoactivity of endothelin-1 after exposure to oxygen.

Endothelin-1 (ET-1) caused a dose-dependent contraction of porcine coronary arterial rings. Preincubation of ET-1 in oxygenated Krebs solution at 37 degrees C resulted in a progressive loss of the contractile activity and immunoreactivity of ET-1. The half-life of ET-1 contractile activity in oxygenated and non-oxygenated buffer was 16.1 and 86.6 min., respectively. The molecular weight of ET-1 exposed to oxygen was identical to that of ET-1. These results indicate that during the contraction of smooth muscle preparations the levels of ET-1 in the tissue bath are steadily decreasing due to exposure to high pO2 levels.