Abstract: AIM: To observe the effects of bupivacaine at different concentrations on intracellular free Ca²⁺ concentration([Ca²⁺]_i) in isolated rat ventricular myocytes induced by KCl using/Laser scanning confocal microscope(LSCM), and to investigate the mechanism of cardiotoxicity of bupivacaine. METHODS: The cultured ventricular myocytes of newborn rats were divided randomly into 4 groups:the control group (group C), the group of bupivacaine at 10 μmol/L (group B₁), the group of bupivacaine at 50 μmol/L (group B₂) and the group of bupivacaine at 100 μmol/L (group B₃).The fluorescent intensity (FI) of intracellular Ca²⁺ in single cultured cardiomyocytes of newborn rats loaded with Fluo-3 AM was observed by LSCM in order to compare the effects of bupivacaine at different concentrations on the change of [Ca²⁺]_i induced by KCl. RESULTS: There was no difference in the changes of intracellular Ca²⁺ FI in rat ventricular myocytes induced by KCl in group B₁ compared with those in group C(P>0.05).Intracellular Ca²⁺ FI in rat ventricular myocytes induced by KCl was inhibited significantly in group B₂ and B₃ compared with that in group C(P<0.05). CONCLUSION: There is no significant effect of bupivacaine at low concentration on intracellular Ca²⁺ in rat ventricular myocytes induced by KCl.Bupivacaine at high concentraton could significantly inhibit the effects on [Ca²⁺]_i in rat ventricular myocytes induced by KCl.Bupivacaine could inhibit Ca²⁺ transsarcolemmal influx in isolated rat ventricular myocytes dosedependently, which may in part explain its negative inotropic effect.

Key words: bupivacaine, ventricular myocytes, laser scanning confocal microscope, intracellular Ca²⁺, Fluo-3