OBJECTIVE: Our purpose was to study the acute effects of 17 beta-estradiol on mechanical and electrical activities of cardiac function and on coronary arteries in the rat heart. STUDY DESIGN: The effects of 17 beta-estradiol were studied on perfused working heart isolated from Charles River male rats. Heart rates, coronary flow, aortic flow, and left ventricular pressure were measured. To avoid coronary interaction, chronotropic and inotropic effects were also tested on isolated atria. Data were analyzed with the paired Student t test. RESULTS: 17 beta-Estradiol produced a dose-dependent negative chronotropic effect in right atria but did not affect the contractility of left atria. A decrease in heart rate was also observed in perfused hearts treated with 5 x 10(-6) mol/L 17 beta-estradiol. 17 beta-Estradiol (5 x 10(-6) mol/L) significantly increased coronary flow (p < 0.005) but had a negligible effect on cardiodynamic index values. A significant effect of 17 beta-estradiol on cardiac function was observed when coronary arteries were precontracted with acetylcholine. CONCLUSION: Both the experimental coronary vasodilatory effect and the negative chronotropic effect of 17 beta-estradiol support the clinical observations that suggest that this hormone may have an important role in prevention of cardiovascular diseases.
OBJECTIVE: Our purpose was to study the acute effects of 17 beta-estradiol on mechanical and electrical activities of cardiac function and on coronary arteries in the rat heart. STUDY DESIGN: The effects of 17 beta-estradiol were studied on perfused working heart isolated from Charles River male rats. Heart rates, coronary flow, aortic flow, and left ventricular pressure were measured. To avoid coronary interaction, chronotropic and inotropic effects were also tested on isolated atria. Data were analyzed with the paired Student t test. RESULTS:17 beta-Estradiol produced a dose-dependent negative chronotropic effect in right atria but did not affect the contractility of left atria. A decrease in heart rate was also observed in perfused hearts treated with 5 x 10(-6) mol/L 17 beta-estradiol. 17 beta-Estradiol (5 x 10(-6) mol/L) significantly increased coronary flow (p < 0.005) but had a negligible effect on cardiodynamic index values. A significant effect of 17 beta-estradiol on cardiac function was observed when coronary arteries were precontracted with acetylcholine. CONCLUSION: Both the experimental coronary vasodilatory effect and the negative chronotropic effect of 17 beta-estradiol support the clinical observations that suggest that this hormone may have an important role in prevention of cardiovascular diseases.