title: Dose-dependent cardiac effect of oestrogen replacement in mice post-myocardial infarction.
abstract: Hormonal replacement therapy (HRT) has recently been shown to increase the risk of cardiovascular events in women. However, it is not clear whether the adverse effect of HRT is related to dosage and/or the presence of progestin. Using a mouse model of myocardial infarction (MI), we studied the dose-effect of oestrogen replacement on mortality and cardiac remodelling and dysfunction post-MI in the absence of progestin. Six-week-old females were subjected to ovariectomy (OVX). A pellet containing a low, moderate or high dose of 17beta-oestradiol (E(2); 0.42, 4.2 or 18.8 microg day(-1)) or placebo was implanted subcutaneously on the day of OVX. Myocardial infarction was induced 8 weeks later, and cardiac morphology and function were evaluated 8 weeks after MI. We found that E(2) at moderate and high doses adversely affected mortality. A low dose of E(2) that restored plasma oestrogen close to physiological levels had no significant effect on mortality but tended to improve cardiac function and remodelling, associated with reduced fibrosis and increased capillary density. At the moderate dose, E(2) exacerbated cardiac fibrosis, hypertrophy, dysfunction and dilatation, associated with liver and kidney enlargement and ascites. Protein kinase C and extracellular signal-regulated kinase were increased by MI but were not affected by E(2). In summary, E(2) at a low dose tended to be cardioprotective. At increased doses that raised plasma oestrogen far beyond the physiological level, E(2) was detrimental to the heart. Our data suggest that dosage should be an important consideration when studying the effect of oestrogen replacement on the heart.
authors.affiliation: Hypertension and Vascular Research Division, Department of Medicine, Henry Ford Hospital & Wayne State University, 2799 West Grand Boulevard, Detroit, MI 48202, USA.
authors.forename: Enbo
authors.initials: E
authors.lastname: Zhan
authors.forename: Thomas
authors.initials: T
authors.lastname: Keimig
authors.forename: Jiang
authors.initials: J
authors.lastname: Xu
authors.forename: Edward
authors.initials: E
authors.lastname: Peterson
authors.forename: Jennifer
authors.initials: J
authors.lastname: Ding
authors.forename: Fangfei
authors.initials: F
authors.lastname: Wang
authors.forename: Xiao-Ping
authors.initials: XP
authors.lastname: Yang
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D015914:Estrogen Replacement Therapy; D004967:Estrogens / Q000097:blood / Q000494:pharmacology*; D005260:Female; D006321:Heart / Q000187:drug effects*; D051379:Mice; D008810:Mice, Inbred C57BL; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009203:Myocardial Infarction / Q000378:metabolism* / Q000401:mortality / Q000473:pathology*; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D010052:Ovariectomy; D011493:Protein Kinase C / Q000378:metabolism; D013739:Testosterone / Q000097:blood
chemical_list: D004967:Estrogens; D013739:Testosterone; D011493:Protein Kinase C; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3