Endothelin ... ET
- Family of 21 amino acids vasoconstrictors peptides
- three isoforms ET-1 ET-2 ET-3
- mediate their actions via two receptors ET-A ET-B
- ET-1 id the most potent
- ET-1 .....the major source is enfothelial cells then macrophages, fibroblast, cardiac myocyte, and neurons
- ET-2 ......Expressed in intestinal cells and at lower level in the heart
- ET-3 .....Expressed in brain neurons, kidney, and intestinal epithelial cells
- ET-2 & ET-3 differ from ET-1 in two and six amino acid repectively
- endothelin show very close structral and functional relationship to the snake venom peptide
- endothelins are released in the form of preproendothelin then undergone sequential prolytic processing by endothelin converting enzyme ECE
- ET-1 & ET-2 have the same affinity to ET-A but duffer to ET-B
- ET-3 binds to ET-B receptor so hence can be considered selective ET-B
