Effects of estrogen on venous function in rats with chronic heart failure

The effect of 17 beta-estradiol on venous function was investigated in ovar iectomized rats with heart failure. Rats (50-60 days old) were ovariectomiz ed and implanted with 60-day-release pellets that contain 17 beta-estradiol (1.5 mg) or vehicle. The left coronary artery was ligated 7 days later. An other group of ovariectomized rats was given vehicle pellets and then a sha m operation was performed. The rats were studied while under pentobarbital anesthesia at 7 wk after ligation. Ligated rats, relative to sham groups, h ad lower mean arterial pressure (MAP, -34 mmHg) and cardiac output (CO, -38 %); higher arterial resistance (R-A, +12%) and venous resistance (R-V, +116 %); mean circulatory filling pressure (MCFP, +40%) and left ventricular end -diastolic pressure (LVEDP, +11 mmHg); and similar cardiovascular responses to norepinephrine (NE). Treatment of ligated rats with 17 beta-estradiol i ncreased CO (+16%); reduced R-A (-16%), R-V (-35%), MCFP (-23%), and LVEDP (-3 mmHg); and augmented MAP, R-V, and MCFP responses to NE. Therefore, 17 beta-estradiol reduced MCFP, and this reduced preload (LVEDP). 17 beta-Estr adiol decreased R-V, which, along with decreased R-A (afterload), led to an increase in CO. 17 beta-Estradiol likely augmented vasoconstriction to NE through an improvement on the cardiovascular status.