The Role of 17β-Estradiol in Myocardial Hypertrophy in Females in the Presence and Absence of Hypertension.

PURPOSE: There are gender-differences in the development of cardiac hypertrophy, which appear to be related, in part, to sex hormones. This report gives an overview of this relationship and reports on original data assessing how varying levels of plasma 17β-estradiol determine relative heart size, in vivo function, in hypertensive versus normotensive rats.

METHODS

Female spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats were either surgically neutered or sham operated at 21 days of age. A subgroup of neutered females received 17β-estradiol replacement. At 6 months, in vivo heart function was measured, the heart/body weight ratio (mg/g) was assessed as a measure of hypertrophy and correlated with plasma 17β-estradiol.

RESULTS

There was a significant positive relationship between plasma 17β-estradiol and heart/body weight ratio in both WKY (R = 0.509, P = 0.011) and SHR females (R = 0.359, P = 0.032). Interestingly, the slope of this relationship was 2-fold steeper in the WKY females, suggesting a blunted effect in the SHR, whose hearts also had 35 % lower ERβ content. With increasing plasma estradiol levels, WKY females showed improved LV function while SHR females showed impaired LV relaxation.

CONCLUSIONS

Plasma estradiol modulates relative heart mass in both normotensive and hypertensive female rats. With any increase in plasma 17β-estradiol, hypertensive females show a blunted response compared with the normotensive females, which may be related to a reduced estrogen receptor expression in the presence of hypertension. In contrast to normotensive females, hypertensive females showed impaired function with increases in plasma 17β-estradiol.