| Objective: To investigate the vasodilative roles and the possible mechanisms of Losartan or Captopril on different vascular rings of rats.Methods: Isotonic tension of different vascular rings precontracted by phenylephrine (PE, 1μmol·L-1) or KCl (60 mmol·L-1) or U46619(1μmol·L-1)was recorded. The vasorelaxing action of Losartan or Captopril and the influence of various drugs on them were observed in the rings with endothelium intact .Results: Losartan or Captopril caused concentration-dependent relaxation in coronary artery precontracted by U46619 and renal artery rings precontracted by PE, and there was significant difference between them. Losartan attenuated the contractile response to KCl in coronary artery and renal artery rings, Captopril did not modify the contractile response to KCl . As pretreatment with the NO synthesis inhibitor L-NAME also reverses the altered vasoconstrictor response to either phenylephrine or U46619 induced by losartan not by Captopril. Cyclo-oxygenase inhibitor indomethacin also diminished the vasorelaxing action of losartan or Captopril in coronary artery and renal artery rings precontracted by PE or U46619 .but Indo had no significant effect on the vasorelaxing action of losartan when the dose of. Losartan is 10-4mol/l.Conclusion: In view of the present results, it can be concluded that in coronary artery and renal artery rings The vasorelaxing action of losartan or Captopril is dose-dependent and associated with prostacyclin, PGI2. In addition, the presence of NO seems to be necessary for the full expression of the effect of losartan on the contractile response to vasoconstrictors in coronary artery and renal artery rings... |
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