ACUTE EFFECTS OF 17-BETA-ESTRADIOL ON THE RAT-HEART

OBJECTIVE: Our purpose was to study the acute effects of 17 beta-estra diol on mechanical and electrical activities of cardiac function and o n coronary arteries in the rat heart. STUDY DESIGN: The effects of 17 beta-estradiol were studied on perfused working heart isolated from Ch arles River male rats. Heart rates, coronary flow, aortic flow, and le ft 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-E stradiol produced a dose-dependent negative chronotropic effect in rig ht atria but did not affect the contractility of left atria. A decreas e 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) s ignificantly 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 c oronary vasodilatory effect and the negative chronotropic effect of 17 beta-estradiol support the clinical observations that suggest that th is hormone may have an important role in prevention of cardiovascular diseases.