Contractile Response of Human Omental Arteries to Endothelin

The effects of endothelin have been studied in isolated arterial segments (0.8-1 mm in external diam.) of human omental arteries obtained during the course of abdominal operations (15 patients, 7 men and 8 women). Paired segments, one normal and the other de-endothelized, were mounted for isometric recording of tension in organ baths. Endothelin produced concentration-dependent contractions with an EC50 value of 5.4 x 10(-9) M. Removal of endothelium did not affect significantly endothelin-induced contractions (EC50, 6.7 x 10(-9) M). Removal of extracellular calcium or addition of the calcium channel blocker nicardipine (10(-6) M) diminished but did not abolish responses to endothelin. These results indicate that endothelin exerts powerful contractile effects on human isolated omental arteries which are independent of the presence of an intact endothelial cell layer; this contraction cannot be explained solely by voltage-dependent calcium channels.