Abstract: Obective To investigate the change expression of neuregulin-1β(NRG-1β) at mRNA and protein levels in myocardium of hypertrophic rats induced by pressure-overloaded．Methods Wistar rats were randomly divided into four groups: myocardial hypertrophy groups (Model) of 4 weeks and 8 weeks, control operation groups (Control) of 4 weeks and 8 weeks. Model groups were operated with abdominal aortic constriction. Hemodynamic and echocardiogrophic characteristics were evaluated; masson staining was employed to observe the pathological lesions of myocardial tissues; radioimmunological method was used to detect angiotensin II (AngII); expression of NRG-1β mRNA and protein in myocardium were tested by Real time-PCR and western blot. Results (1) Compared with 4wC, left ventricular ejection fraction (LVEF)、left ventricular fraction shortening (LVFS)、left ventricular end systolic pressure (LVESP)、Maximal rate of increase in left ventricular pressure (±dP/dtmax) of 4wM were decreased（P <0.05），while left ventricular end-systolic diameter (LVEDD)、left ventricular end-diastolic diameter (LVESD)、left ventricular end diastolic pressure (LVEDP) 、 collagen volume fraction (CVF) and AngII of 4wM were increased（P <0.05，P <0.01），NRG-1β mRNA and protein expression of 4wM group were not exchanged（P >0.05）。 (2) Compared with 8wC, LVEF、LVFS、LVESP、±dP/dtmax of 4wM were decreased（P <0.01）, LVEDD、LVESD、LVEDP、CVF and AngII were increased（P <0.05，P <0.01），NRG-1β mRNA and protein expression of 8wM group were decreased（P <0.01）。Conclusion The expression of NRG-1β in myocardium of hypertrophic rats induced by pressure-overloaded are down-regulated ，which may be involved in the myocardial hypertrophy development.

Key words: Key word: NRG-1β, pressure-overload, myocardial hypertrophy