The vasoactive properties of endothelin-1 (ET-1) in the animal model v
ary with the tone of the pulmonary vessels, the dose level of ET-1, an
d the maturation of the vessels. The action of ET-1 is mediated by end
othelium-derived nitric oxide, prostaglandins, and electrolytes. Plasm
a levels of ET-1 are elevated in pulmonary hypertension in both animal
s and humans. ET-1 antagonists may prove useful in treating pulmonary
hypertension in children and adults.