Objective: To evaluate the effect of urotensinⅡ(UⅡ) on the systemic and pulmonary
hemodynamics and the antagonism of N G
-nitro-L-arginine methyl ester(L-NAME) to UⅡ in normal rats. Methods: Different concentrations of UⅡ(0.1～30.0 nmol·kg -1 ) or an equal volume of saline was injected into pulmonary artery of normal rats, The group of L-NAME was given UⅡat 10 min following pretreatment with L-NAME, then the hemodynamic response to U Ⅱ(10 nmol.kg -1 ) was observed. Results: The
pulmonary arterial injection of UⅡ(0.1～30.0 nmol· kg -1 ) induced decrease in systolic pressure(SP),diastolic pressure(DP), mean carotid arte- rial pressure(mCAP) with the increase of UⅡ concentrations. The depressor response to UⅡ (10 nmol·kg -1 ) was attenuated by approximatel 60% through pretreatment with L-NAME, but no effects of pulse pressure(PP),mean pulmonary arterial pressure(mPAP) and heat rates (HR) were observed. Conclusion: The results suggest that the pulmonary arterial injection of U Ⅱ cause dose-dependent decrease in SP、DP、mCAP and the depressor response to UⅡ be partially mediated via L-arginine/NO pathway.