Endothelial cells produce not only relaxing factors, but in certain conditions they can induce the synthesis of contracting factors including cyclooxygenase derivatives such as prostanoids or superoxide anions. In agreement with experimental data, these cyclooxygenase-dependent endothelium-derived contracting factors (EDCFs) are responsible for impaired endothelium-dependent vasodilation to acetylcholine in patients with essential hypertension, but not in those with hypertension secondary to primary aldosteronism or renovascular disease. However, EDCF production is a phenomenon that occurs during aging, and hypertension merely causes an anticipation and worsening of this alteration. It is worth noting that in both normotensive subjects and essential hypertensive patients, the age-related appearance of EDCFs is associated with a parallel impairment in nitric oxide (NO) availability. This suggests that the EDCFs are oxygen free radicals, In agreement with this possibility, the antioxidant vitamin C increases the vasodilation to acetylcholine in essential hypertensive patients by restoring NO availability. However, in the presence of cyclooxygenase blockade by indomethacin the facilitating effect of vitamin C on the response to acetylcholine is prevented, thereby suggesting that cyclooxygenase is the main source of oxidative stress in essential hypertension. Another clinical condition characterized by cyclooxygenase-dependent EDCF production is acute estrogen deprivation. In normotensive women, ovariectomy and the consequent acute estrogen deprivation causes impaired endothelium-dependent vasodilation characterized by the simultaneous presence of an impairment in the NO system and the production of cyclooxygenase-dependent EDCFs which, even in these conditions, are very likely to be oxygen free radicals. In conclusion, cyclooxygenase-dependent EDCF production is characteristic of aging and different conditions such as the presence of essential hypertension or endogenous estrogen can alter the appearance and degree of synthesis of these substances in opposite ways.
|Autori:||Taddei S; Virdis A; Ghiadoni L; Sudano I; S.Buralli; Salvetti A.|
|Titolo:||Cyclooxygenase-dependent endothelium-derived contracting factors.|
|Anno del prodotto:||1998|
|Appare nelle tipologie:||1.1 Articolo in rivista|