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

The effect of 17beta-estradiol on venous function was investigated in ovariectomized rats with heart failure. Rats (50-60 days old) were ovariectomized and implanted with 60-day-release pellets that contain 17beta-estradiol (1.5 mg) or vehicle. The left coronary artery was ligated 7 days later. Another group of ovariectomized rats was given vehicle pellets and then a sham operation was performed. The rats were studied while under pentobarbital anesthesia at 7 wk after ligation. Ligated rats, relative to sham groups, had 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 17beta-estradiol increased 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, 17beta-estradiol reduced MCFP, and this reduced preload (LVEDP). 17beta-Estradiol decreased R(V), which, along with decreased R(A) (afterload), led to an increase in CO. 17beta-Estradiol likely augmented vasoconstriction to NE through an improvement on the cardiovascular status.