Effect of reptilase on the contraction of rat thoracic aorta circle in vitro

Objective:To explore the effect of reptilase(RTA)on the contraction and mechanism of thoracic aorta isolated from rats.Methods:After preparation of the rat thoracic aorta rings,the tension of the rings was measured by biological signal analytical system.The two groups of endothelium-denuded aorta rings and endothelium-intact aorta rings were undergone cumulative dose increase of the drug for observing effects of reptilase on the contraction of isolated rat thoracic aorta circle pretreated by phenylephrine(PE)and potassium chloride(KCl),respectively.Results:Reptilase resulted in concentration-dependent contraction of the aorta rings pre-constricted by PE.The contraction induced by PE was much stronger in the group of endothelium-intact than in endothelium-denuded aorta rings,but no significant difference was found for the contraction induced by KCl in the two groups.On observation of the vessels with intact endothelium undergone pre-incubation of endothelin converting enzyme inhibitor phosphoramidone(PAMD,5×10-6 mmol/L),reptilase showed weaker enhancement to PE-induced contraction as compared with that free of incubation(P0.01).The endothelium-denuded vascular rings,after chelating extracellular Ca2+ or LaCl3 by EDTA,markedly inhibited the enhancement of reptilase to PE-induced contraction.Conclusion:Reptilase may cause concentration-dependent contraction of aorta rings pre-constricted with PE.The mechanism may be attributable to involvement of endothelial cells to provoke the release of endothelin through vascular constriction induced by PE.Still,It may also be involved in the receptor-operated calcium channel in the vascular smooth muscle,which can promote the calcium influx of vascular smooth muscle.