[Release of endothelin from isolated perfused human umbilical vein. I: Effect of ionomycin]

Endothelin-like immunoreactivity (ET-LI) was directly measured in the perfusate from the isolated human umbilical vein perfused with Krebs-Ringer solution. The identity of the immunoreactive peptide was confirmed as ET-1 by high-performance liquid chromatography. The rate of release of ET-LI was 86.7 +/- 25.9 (SE) fmol during the first perfusion period of 30 min, and it remained stable at least for 4 hours. Calcium ionophore ionomycin, added to the perfusion medium (10(-7)-10(-6) M), stimulated the ET-LI release in a dose-dependent fashion; it increased the rate of release by 29.1% and 143.4% over the control at the concentrations of 10(-7) and 10(-6) M, respectively. These results taken together with previous observations of synthesis of ET in cultured vascular endothelium provide direct evidence for local generation and subsequent release of ET from vascular beds of human beings.