Aim To observe the effects of norepinephrine (NE) and α1-adrenergic receptor antagonist prazosin on Ca2+-ATPase activity and mRNA expression of PMCA1 in cultured thoracic aortic smooth muscle cells (ASMC) isolated from spontaneously hypertensive rats (SHR).Methods ATPase activity in cultured ASMC was determined by spectrophotometry and mRNA expression of PMCA1 was measured by semiquantitative reverse transcription polymerase chain reaction (RT-PCR).The effects of different doses of NE and prazosin on ATPase activity and mRNA level of PMCA1 in ASMC were observed.Results NE(10-7 mol/L)significantly attenuated the ATPase activity(P<0.01) and mRNA expression of PMCA1(P<0.01).Compared with SHR control,10-5 mol/L and 10-6 mol/L prazosin attenuated the repressed effect of 10-7 mol/L NE on Ca2+-ATPase activity (P<0.05).10-6 mol/L prazosin could repress the effect of 10-7 mol/L NE on mRNA expression of PMCA1(P<0.05).The ATPase activity and mRNA expression of PMCA1 in ASMC had no alteration after intervened by prazosin(P>0.05).Conclusions NE can attenuate the ATPase activity and mRNA expression of PMCA1 which may be through the pathway of α1-AR and mediate the downregulation of genetic transcription.Prazosin can inhibit the effect of NE on attenuating the Ca2+-ATPase activity and mRNA expression of SHR ASMC through blocking the α1-AR pathway.Prazosin had no effect on the activity and mRNA expression of PMCA1.