Objective To investigate the protective effects of antioxidant taurine plus metoprolol on the blood pressure(BP)and blood vessel function of elderly spontaneously hypertensive rats(SHR).Methods SHRs were divided into three groups (6 rats,each):metoprolol group (100 mg · kg-1 · d-1,intragastric administration);taurine group (200 mg · kg-1 · d-1,intraperitoneal injection);taurine plus metoprolol group(metoprolol 100 mg· kg-1 · d-1,intragastric administration ± taurine 200 mg· kg-1 · d-1,intraperitoneal injection).The control group[6 Wistar-Kyoto(WKY) rats]was treated with the same volume of sterile normal saline on the same schedule in intragastric administration and intraperitoneal injection.Blood pressure variability(BPV),diurnal variation of BP,the level of glutathion peroxidase (GSH-Px),malonaldehyde (MDA) and the aorta GSTM1 enzyme expression were evaluated before and 14 days after treatment.Results The serum GSH-Px activities were higher in metoprolol group[(2 759.8 ± 117.6) kU/L],taurine group [(2 848.0 ± 280.2) kU/L] and taurine plus metoprolol group[(3 052.8±283.7)kU/L]than in control group[(2 368.0± 60.4) kU/L] (all P＜0.05).Fourteen days after treatment,MDA level was significantly lower in taurine group[(9.5±0.7)ng/L,P＜0.01]than in control group[(13.7±1.5)ng/L].However,there was no statistical difference in MDA level between metoprolol group/taurine plus metoprolol group and control group.Forty weeks after treatment with taurine,GSTM1 protein expression was increased,but it had no statistical difference.Conclusions The combined antioxidant taurine and metoprolol can effectively decrease BPV of elderly SHRs,in which the antioxidant effect might be associated with elevated GSTM1 protein expression.