Protective Effect Of Astragalus Polys-accharides On Isoprotereno-induced Myocardial Hypetrrophy In Neonatal Rats

ObjectiveTo investigate the effect and mechanism of Isoproterenol-induced neonatalrat cardiomyocyte hypertrophy by Astragalus Polysaccharides（APS）, especiallyfor the Ca²⁺/CaN signal transduction.MethodsMyocardial cells of neonatal rat were cultured in vitro. To define the effectsof APS on cardiac hypertrophy the hypertrophic cardiac myotecytes wereinduced by isoproterenol10μmol·L^-1.Cardiomyocyte cells were randomized intoeight groups: normal control group; Iso group; CsA group; Iso+CsA group; Iso+APS0.1,1,10mg.L^-1group; Iso+Verapamil group.Total protein content wasassayed by Bradford Protein Assay Kit; the size of cardiomyocytes wasmeasured by computer photograph analysis system; the cardiomyocyte viabilitywas analysed by MTT assay; the expression of ANP mRNA was determined byRT-PCR; Intracellular [Ca²⁺]ichanges was measured by confocal lasermicroscopy and by cell-loading Fluo-3/AM;the expression of CaN wasmeasured by Western blot.ResultsCompared with normal control group, Iso10μmol·L^-1significantlyincreased the total protein content and size of cardiomyocoytes cell by 56.7%,81.3%, reduced the cardiomyocyte viability by46.6%,and significantlyincreased the [Ca²⁺]iconcentration,the expression of CaN and ANP weresignificantly increased （P<0.01）. After pretreatment with APS, the totalprotein content and cardiomyocoyte cell size were reduced （P<0.01orP<0.05）,[Ca²⁺]iconcentration and the expression of CaN and ANP were asloreduced（P<0.05or P<0.01）, in which APS1,10mg·L^-1group can be restoredto normal levels of the control group（P>0.05）, APS10mg·L^-1could significantlyantagonize the expression of CaN.ConclusionThese in virto results show that APS has protective effect onisoproterenol-induced cardiac hypertrophy, the mechanism may be related toinhibit [Ca²⁺]iand decrease expression of CaN.