Endothelin is a potent constrictor of the lamb ductus arteriosus

Abstract

Endothelin was tested on isolated ductus arteriosus preparations from mature fetal Iambs. At low [Formula: see text] (18–24 Torr; 1 Torr = 133.3 Pa), the compound constricted the vessel dose-dependently over the range from about 10−10 to 10−7 M. The contraction was sustained and did not subside even after an extended period of washing. Endothelin was also effective on tissues ([Formula: see text], 217–231 Torr; indomethacin, 2.8 × 10−6 M) that had been completely relaxed with CO (CO/O2 ratio, 0.28). CO treatment interferes with a cytochrome P-450 mechanism, which is considered crucial for the contractile response of the vessel to oxygen. These findings are consistent with a role of endothelin in the closure of the ductus arteriosus at birth.Key words: ductus arteriosus closure, oxygen, cytochrome P-450.