Objective: To investigation the effect of ropivacaine on the contraction of the isolated human umbilical artery and the mechanisms involved.
Methods: Endothelium-denuded human umbilical artery rings obtained from healthy full-term parturients were prepared. Using isometric force transducers and a fluorometer, the effect of ropivacaine in cumulative concentration on the contraction response induced by KCl in the presence or absence of verapamil, or verapamil plus ruthenium red or verapamil plus heparin was observed. Furthermore, the effect of ropivacaine on the contraction response of the artery rings incubated in different concentrations of extracellular Ca(2+) was also observed.
Results: Ropivacaine induced a dose-dependent biphasic contractile response of human umbilical artery rings: increasing at concentrations of 1.0 x 10(-5) to 1.0 x 10(-4) mol/L and decreasing from 3.0 x 10(-4) to 3.0 x 10(-3) mol/L, which was inhibited by verapamil, or verapamil plus ruthenium red, or verapamil plus heparin. No difference was found between pre-treatment of verapamil, verapamil plus ruthenium red and verapamil plus heparin. Ropivacaine induced no contractile response in Ca(2+)-free solution and a extracellular Ca(2+) dose-dependent increasing contractile response (1.0 x 10(-4) to 3.0 x 10(-2) mol/L).
Conclusion: Ropivacaine induced a dose-dependent biphasic contractile response of human umbilical artery rings. The increase in intracellular Ca(2+) concentrations by the extracellular Ca(2+) influx, not by the release from the sarcoplasmic reticulum, is involved in ropivacaine-induced vasoconstriction of human umbilical artery smooth muscle.