Endothelin system and the role of salt in hypertension

Although hypertension is studied for several decades, this problem is still not solved. Moreover, its incidence increases. Most cases of secondary hypertension is associated with the kidneys, the most important organ regulating the volume and ionic composition of body fluids. If the kidneys are damaged, or intake of salt is excessive, they are unable to fulfill their role and blood pressure (BP) increases. Especially salt contributes to secondary hypertension. Excessive salt intake increases the volume of body fluids and subsequently increases BP, and secondary act on the mechanisms regulating BP, mainly the renin-angiotensin system (RAS) and endotelin (ET) system. Endothelin-1 (ET 1) is the main active peptide of the ET system. ET-1 is one of the most potent vasoconstrictors. It acts through ET receptors type A and B (ETA and ETB receptors), which belong to the family of receptors coupled with G-proteins. The effects of ETA and ETB receptors differ depending on the type of cells where they are located. For example, ETB receptors in vascular smooth muscle contribute to vasoconstriction, whereas the same receptors on endothelial cells of blood vessels mediate vasodilation (stimulating the production of NO). In the kidney, ET system affects excretion of Na+and water and contribute to the regulation..