Increased circulating levels of ET have been observed in patients with several life-threatening diseases, including pulmonary arterial hypertension (PAH). The diverse deleterious effects of ET include vasoconstriction, vascular hypertrophy, cell proliferation, fibrosis, and inflammation.

ET receptors promote different effects depending on the cell type on which they are found. For instance, ET_B receptors promote vasoconstriction and cell proliferation when found on smooth muscle cells, but vasodilation when found on endothelial cells. In pathology, these differences are amplified due to up- and down-regulation.

Because ET is expressed by and its receptors are located on a wide variety of cell types throughout the body, the effects of excess ET in pathology are far-reaching and numerous. Areas of study include the vessels, the heart, the lungs, the skin, the kidneys, and the brain.

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