Purpose. To summarize how abnormal release of relaxing and contracting factors from endothelial cells contribute to the vascular abnormalities in hypertension. Endothelium-derived factors. The endothelium controls the tone of the underlying vascular smooth muscle by releasing relaxing and contracting factors. The former include prostacyclin, nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF), and the latter endoperoxides, thromboxane A2, superoxide anions and endothelin. Hypertension In most types of hypertension, endothelium-dependent relaxations are curtailed, because of a reduced production and/or action of endothelium-derived NO and EDHF. In essential hypertension, endothelium-dependent relaxations are reduced also because of the endothelium-dependent production of vasoconstrictor prostanoids (endoperoxides and, in some cases, thromboxane A2). Cause or consequence. The endothelial dysfunction observed in hypertensive blood vessels is likely to be a consequence rather than a cause of the disease process. Therapeutic implications. Enhanced release of endothelium-derived relaxing factors (NO and EDHF) help to explain the therapeutic effects of inhibitors of converting enzyme.

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