The perfusion pressure ratio, electrical field stimulation(.40 V, 5 msec, 40 Hz, 30 sec)-induced pressure change/norepinephrine(10-´l~l, 15 ml)-induced pressure change, in isolated mesenteric bed was evaluated. Losartan-treated(30 mg; kg/day, 2 weeks) SHR showed decreased perfusion pressure ratio compared with control. To evaluate the cause of the decrease in perfusion pressure ratio we used isolated aorta. Incubation with losartan(10-´NI, 90 min) decreased the contractile response induced by phenylephrine(10-´I~1) and KCI(50 mill) and the decreased response cvas not shown in enalapril treated(5 mg/kg/day, 2 weeks) SHR. Th~~ decreased contractile response by losartan was more prominent in endothelium intact strip and less remarkahle in denuded strip.
Frcm these results we can assume that losartan decreased the contractile response by eliminating local renin angiotensin system, particularly in the endothelium of aorta and therefore by reducing the contraction amplifying effect of angiotensin II.
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