Acute effects of transdermal estradiol administration on plasma levels of NO in postmenopausal women

Objective: To investigate the acute effects of transdermal E2 administration on nitric oxide {NO} plasma levels in postmenopausal women. Design: Randomized, placebo-controlled trial. Setting: Normal human volunteers in an academic research environment. Patient(s): Twenty healthy postmenopausal women. Intervention(s): Transdermal administration of 100 pg/d E2 or placebo. Main Outcome Measure(s): Plasma concentrations of NO stable oxidation products and serum concentrations of E._,were assessed before and 24 hours after the administration. Result(s): In the group treated with E2 mean concentration of NO metabolites 24 hours after patch application (37.31 +_7.62 pmol/L) resulted significantly higher than baseline (21.04 ___5.71 pmol/L) and the control group/23.50 _+4.03 pmol/L). The correlation between the mean percent increase in NO metabolites and absolute E., concentrations 24 hours after the E.~administration was statistically significant. Conclusion(s): Transderma] administration of E2 to healthy postmenopausal women in- creases the plasma levels of NO and this supports the hypothesis that a NO-related mechanism may contribute to the cardiovascular protective effect of estrogens in postmenopause.