Effects Of Sexual Hormones On Cardiac Hypertrophy In SHR Rats And Cultured Cardiomyocytes

Objective:To investigate the effects and potential mechanisms of sexual hormones on cardiac hypertrophy in ovariectomized SHR rats and in AngⅡinduced hypertrophic cultured cardiomyocytes.Methods:In vivo,female SHR rats and WKY rats underwent bilateral ovariectomy were randomly divided into 3 groups（6/group）:ovariectomized rats（OVX）,estrogen-supplemented ovariectomized rats（OVX+E）and testosterone-supplemented ovariectomized rats（OVX+T）with tea oil,estradiol benzoate 0.25mg/（kg.2d）,testosterone propionate 3mg/（kg.2d）intramuscular injection for 8 weeks respectively.Caudal artery systolic blood pressure（SBP）,circulating levels of serum estrogen,testosterone and ANP,Left Ventricular Mass Index（LVMI）were measured.Left ventricular section stained by haematoxylin and eosin,masson trichrome stain was observed for morphological alternations.Collagen volume fraction based on masson trichrome stain is calculated.Protein expression of Akt,phos-Akt^Ser473,ERK,phos-ERK^{Thr202/Tyr204} andβ-MHC in myocardium were measured.In vitro,the H9c2cell line was treated with 100nM AngⅡfor 24 hours to induce hypertrophy and co-treated with 17β-estradiol or testosterone for 24 hours to explore the effects of sexual hormones on hypertrophic cells.Pre-treated with PD98059 for an hour before treated with AngⅡand sexual hormones was to find out the relation of MEK/ERK signaling pathway in hypertrophy.As hypertrophy related indicators,cell surface area,total protein,mRNA expression of ANP andβ-MHC,protein expression ofβ-MHC,were measured.The protein expression of Akt,phos-Akt^Ser473,ERK,phos-ERK^{Thr202/Tyr204} were detected.Results:Ovariectomized rats with testosterone supplement resulted in SBP increase compared with other groups（P<0.05）.Haematoxylin and eosin stain and LVMI,ANP levels andβ-MHC expression which represented hypertrophy and masson trichrome stain with CVF which represented cardiac fibrosis were aggravated in group OVX+T while these parameters were improved in group OVX+E in SHR rats.Western blot demonstrated that phos-Akt expression was decreased and phos-ERK expression increased in ovariectomized SHR rats.Estrogen supplement reduced phos-ERK expression and increased phos-Akt expression while androgen supplement generated opposite effects.In vitro,AngⅡtreated for 24 hours increased hypertrophy related indicators and protein expressions of phos-ERK and phos-Akt.Co-incubation with17β-estradiol could significantly inhibit the enlargement of cell area and related markers of hypertrophy induced by AngⅡwhile co-incubation with testosterone could aggravate the detections mentioned above except cell size.Further study revealed that pre-treated with PD98059 for an hour before treated with AngⅡreduced cell size,totol protein and mRNA ANP.PD98059 significantly reduced hypertrophic markers induced by testosterone and AngⅡ.PD98059 had no effect on improvement alleviated by 17β-estradiol.Conclusion:Estrogen can improve cardiomyocytes hypotrophy while androgen exacerbate it.ERK and Akt signaling pathways may participate in formation of hypotrophy induced by hypertension and AngⅡor effects on hypotrophy by sexual hormones.