Figure 1410

Regulation of endothelin (ET) action; the role of the ET receptors. Pre-pro ET is produced and converted to big ET. Big ET is converted to mature, active ET by endothe-lin-converting enzyme (ECE) present on the endothelial cell membrane. Mature ET secreted onto the basolateral aspect of the endothelial cell binds to two ET receptors (ETa and ETb); both are present on vascular smooth muscle (VSM) cells. Interaction of ET with predominantly expressed ETa receptors on VSM cells induces vasoconstriction. ETB receptors are predominantly located on the plasma membrane of endothelial cells. Interaction of ET-1 with these endothelial ETB receptors stimulates production of nitric oxide (NO) and prosta-cyclin by endothelial cells. The production of these two vasodilators serves to counterbalance the intense vasoconstrictor activity of ET-1. PGI2—prostaglandin I2.

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