Abstract: AimTo investigate the hypersensitization of α-adrenoreceptor of artery smooth muscle in hypertensive patients and rats and the mechanisms concerned. MethodsIsometric tension of artery ring segments was recorded by a sensitive myograph system in vitro and the relative amount of α-adrenoreceptor mRNA was quantified by a real-time PCR. ResultsNoradrenaline (NA)-induced concentration-contraction curve of mesenteric artery segments in spontaneously hypertensive rats (SHR) was more potent than that in Wistar-Kyoto (WKY) rats. The E_max of NA in SHR was 1.82 times of that of WKY. The concentration-contractile curve induced by NA in great omental arteries of hypertensives significantly shifted toward left and the pD₂ value of NA was larger than that of normotensives. After organ culture, the concentration-contractile curves of SD rat mesenteric artery induced by NA shifted toward left with significantly increased E_max. The relative amounts of mRNA for α₁-adrenoreceptor was increased, but mRNA level for α₂-adrenoreceptor did not change. ConclusionThe sensitivity of α₁-adrenoreceptor of artery smooth muscle in hypertensive man and rat is enhanced, suggesting α₁-adrenoreceptor is up-regulated.