OBJECTlVE To investigate the action mechanism of antidepressant fluoxetine on hERG ( ether-a-go-go-related gene ) potassium channel, and the effect of protein kinase C ( PKC ) agonist phorbol-12-myristate-13-acetate ( PMA) on fluoxetine inhibition. METHODS The whole cell patch clamp technique was used to record the change in hERG potassium current ( IKr ) on HEK293 cells that stably expressed hERG potassium channel ( hERG-HEK293 steady-state cells) , which was treated with fluoxe-tine 0.01, 0.1, 1 and 10μmol·L-1 , to study the concentration-and voltage-dependence of the effects on IKr, and to observe the changes in activation, inactivation and recovery dynamics of hERG potassium channel treated with fluoxetine 1μmol·L-1 . On this basis, the effect of PMA of 1μmol·L-1 on inhibition of fluoxetine 1 μmol·L-1 was explored. RESULTS Fluoxetine 0.01, 0.1, 1 and 10 μmol·L-1 inhibited IKr on hERG-HEK293 steady-state cells in a concentration- and voltage-dependent manner. The half maximal inhibitory concentration ( lC50 ) was about 0. 8 mmol·L-1 , and the Hill coefficient was about 1. 1. Fluoxetine 1 μmol·L-1 could reduce the activation, deactivation and recovery currents of IKr and affect the activation and recovery of hERG potassium channel. After fluoxetine inhibition of IKr became stable, PMA 1 μmol·L-1 could inhibit the blocking effect of fluoxetine on hERG potassium channels. CONCLUSlON Fluoxetine has obvious inhibitory effect on IKr of hERG-HEK293 steady-state cells, but the effect could be inhibited by PKC agonist PMA.

OBJECTlVE To establish a real-time cell analysis system ( RTCA) for early drug car-diotoxicity evaluation. METHODS An in vitro drug cardiotoxicity evaluation method was established using RTCA Cardio system and primary cultured cardiomyocytes of neonatal rats. The beating rate, am-plitude and beating rhythm irregularity ( BRl ) of cardiomyocytes were observered after antiarrhythmic drugs, such as quinidine and lidocaine were added, to assess the effect of the above method on cardio-toxicity evaluation. RESULTS RTCA Cardo E-Plate 96 was inoculated with primary cultured cardiomyo-cytes that began to beat after 24 h and beat regularly after 48 h. The stable beating was maintained for a minimum of three days. The beating of cardiomyocytes decreased rapidly from 155±5 to 0 after incuba-tion with quinidine. The beating recovered gradually after 6 h. Quinidine at 3.1μmol·L-1 caused the beat-ing rate to return to 124±16. Quinidine allowed the beating rate to return to normal when the concentra-tion was less than 100.0μmol·L-1 . The beating rate, amplitude and BRl of cardiomyocytes changed in a concentration-dependent manner when incubating with lidocaine. The higher the concentration, the more significant the inhibition of lidocaine on cardiomyocytes. CONCLUSlON The cardiotoxicity of quinidine and lidocaine can be detected accurately using RTCA Cardio system, suggesting that this system can be used in early evaluation of drug cardiotoxicity.