Endothelin has potent inotropic effects in rat atria.

Endothelin, a novel peptide recently isolated from aortic endothelial cells, is one of the most active vasoconstrictors yet characterized. We report that endothelin is also a very potent inotropic substance, as demonstrated in isolated rat heart atria. The effects were observed at nanomolar concentrations and appeared to be due to a direct action of the peptide on the heart muscle cells. Thus, endothelin is not only a powerful vasoconstrictor but also has potent contractile effects on cardiac myocytes.