title: The Role of 17β-Estradiol in Myocardial Hypertrophy in Females in the Presence and Absence of Hypertension.
abstract: OBJECTIVE
  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.
authors.affiliation: From the Departments of Physiology (J.W., C.W., M.B) and Surgery (C.W.) and The Cardiovascular Sciences Collaborative Program (W.J.W., C.W.), University of Toronto, 1 King's College Circle, Medical Sciences Bldg. Room 7256, Toronto, Ontario, Canada, M5S 1A8, c.wittnich@utoronto.ca.
authors.forename: Carin
authors.initials: C
authors.lastname: Wittnich
authors.forename: Jack
authors.initials: J
authors.lastname: Wallen
authors.forename: Michael
authors.initials: M
authors.lastname: Belanger
mesh_terms: D000818:Animals; D001835:Body Weight; D006332:Cardiomegaly / Q000097:blood* / Q000378:metabolism; D004958:Estradiol / Q000097:blood*; D047628:Estrogen Receptor alpha / Q000378:metabolism; D047629:Estrogen Receptor beta; D005260:Female; D006973:Hypertension / Q000097:blood* / Q000378:metabolism; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY
chemical_list: D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D004958:Estradiol