Endothelium-dependent Vasodilation in Hypertension: A Review

Using both in vitro and in vivo techniques, it has repeatedly been shown that endothelium-dependent vasodilation (EDV) is impaired in different forms of experimental hypertension (SHR, Dahl salt-sensitive rat, DOCA-salt rat and renovascular hypertension). EDV has also been found to be impaired in primary, as well as in secondary forms of human hypertension. Although impaired EDV is a general finding in hypertension, the pathophysiological mechanisms might differ between different forms of hypertension and between different types of vessels and vascular beds. Impaired activity of nitric oxide synthase, increased release of endothelin-1, increased production of a prostanoid-derived contracting factor, decreased generation of endothelium-derived hyperpolarizing factor/s and impairment caused by superoxide ions have all been shown to contribute to the impairment of EDV during different conditions. While most antihypertensive treatments improve EDV in experimental hypertension, no uniform picture has been seen in human hypertension, possibly because different antihypertensive drugs have different direct actions on EDV. This review shows that while impaired EDV has been found to be a general feature of hypertension, the mechanisms involved and the therapeutic opportunities have still to be established.