Rapid potentiation of endothelium-dependent vasodilation by estradiol in postmenopausal women is mediated via cyclooxygenase 2.

Estrogens influence cardiovascular function through direct and indirect effects and via genomic and nongenomic mechanisms. The pathways underlying the nongenomic mechanisms are not completely understood. Estrogen-induced responses in vascular cells have been shown to influence prostaglandins and cyclooxygenase (COX), a key enzyme in the production of prostaglandins, with two isoforms, COX-1 and COX-2. We investigated the effects of prostaglandins on the acute potentiation by 17beta-estradiol (E) of acetylcholine (ACh)-mediated vasodilation in the cutaneous vasculature. Using a double-blind placebo-controlled design, we assessed skin blood flow in 32 healthy, postmenopausal women by laser Doppler velocimetry with direct current iontophoresis of ACh and sodium nitroprusside before and after 6-wk treatment periods with aspirin (a nonspecific COX-1 and COX-2 inhibitor), diclofenac (predominantly a COX-2 inhibitor, which also inhibits COX-1), celecoxib (a specific COX-2 inhibitor), given at anti-inflammatory doses, or placebo. Blood flux values before iontophoresis of ACh did not differ between the treatment groups or after E administration, excluding a direct cutaneous vasodilator effect of the treatments or of E. Acute E administration enhanced the response to ACh after aspirin, diclofenac, and placebo; however, this effect was completely abolished with celecoxib treatment (P < 0.05). E had no effect on sodium nitroprusside-mediated vasodilation after any of the treatments. We conclude that the COX-2 pathway plays a specific role in the rapid E-induced potentiation of cholinergic vasodilation in postmenopausal women.