OBJECTIVETo investigate the changes in renin angiotensin system (RAS) in hypertrophied myocardium of spontaneous hypertensive rat (SHR), and the effect of Banxia Baizhu Tianma Decoction (BBTD) on the changes in haemodynamic parameters and mRNA of signaling molecules of RAS at different periods.

METHODSFifty-four male SHRs of 6 weeks old were randomly and equally divided into three groups: the untreated control group, the test group, and the positive control group, and they were treated respectively with distilled water, BBTD and captopril by dissolving in equal volume of water administrated via gavage for 18 weeks. Besides, 18 age matched Wistar-Kyoto (WKY) rats treated with distilled water were allocated in a normal control group. Rats were managed in batches at their age of 18, 24, and 32 weeks old. Rat's hemodynamic parameters were measured through carotid artery catheterization, myocardial pathology was observed, and their mRNA expressions of angiotensin (AGT), angiotensin-converting (ACE) and angiotension-converting 2 (ACE2) were determined by Real-time PCR.

RESULTSCompared with WKY rats, the arterial pressure and left ventricular mass index (LVMI)in SHR were significantly higher at 18, 24 and 32 weeks respectively (P < 0.01); average cycle rate showed in electrocardiogram was higher (P < 0.05), though the blood stream was similar; mRNA expressions of AGT and ACE in heart tissue were markedly higher (P < 0.01), but that of ACE2 at 18 and 24 weeks were lower (P < 0.01). Compared with untreated SHR, arterial pressure at 18 and 24 weeks was lower (P < 0.05); cardiac muscle structure was improved; LVMI at 24 weeks was improved (P < 0.05); the mRNA expressions of AGT and ACE were suppressed but that of ACE2 increased at 18, 24,and 32 weeks significantly in the test group after BBTD treatment (P < 0.05).

CONCLUSIONSChanges in RAS in the hypertrophied myocardium of SHR may be one of the molecular mechanisms for hypertension leading to left ventricular hypertrophy. BBTD can improve the hemodynamic parameters, regulate RAS, so as to lower the arterial pressure.