RESUMEN
OBJECTIVE To explore potential proarrhythmic effect and underlying mechanism of azithromycin (AZM) and Shengmai injection (SM) used clinically.METHODS ① In vivo guinea pig ECG recordings were made to analyze effects of jugular intravenous(iv) injection of AZM [38.2 mg· kg-1,one time (clinically relevant dose,CRD)],or SM (4.6 mL· kg-1,one time CRD) or their combination.②In vitro ECG recordings were made to analyze effects of AZM,SM or AZM + SM on ECG in isolated hearts of guinea pigs.AZM [one,five and ten times (clinically relevant concentrations,CRC)] was perfused in this order:41.5 →207.5 → 415 mg· L-1 and SM (one,five and ten times CRC) in this order:5 →25 →50 mL· L-1.Also,AZM (41.5 mg· L-1,one time CRC) +SM (5 mL· L-1,one time CRC) was perfused to isolated hearts of guinea pigs.③ Enzymatically isolated cardiomyocytes from guinea pig left ventricles were perfused in this order:AZM 41.5 mg· L-1 →AZM 41.5 mg· L-1+SM 5 mL· L-1 for action potential,L-type Ca2+ and Na+ current recordings,respectively.RESULTS ① Neither AZM 38.2 mg· kg-1,nor SM 4.6 mL· kg-1 significantly changed the in vivo ECG.However,AZM 38.2 mg· kg-1 +SM 4.6 mL · kg-1 significantly reduced heart rate (P＜0.05) and prolonged the P-R (P＜0.05) and QRS (P＜0.05) intervals.②AZM 41.5,207.5 and 415 mg· L-1 reduced heart rate (P＜0.05) and prolonged the P-R (P＜0.05) and QRS (P＜0.05) intervals in a concentration-dependent manner.AZM 415 mg·L-1 also prolonged QTc (P＜0.05) interval.SM 5,25 and 50 mL· L-1 reduced heart rate (P＜0.05) and prolonged the P-R interval (P＜0.05) in a concentration-dependent manner.SM had no effect on QRS or QTc intervals.Washout partially recovered the above changes.Moreover,AZM 41.5 mg· L-1 + SM 5 mg·L-1 significantly reduced heart rate (P＜0.05) and prolonged the P-R (P＜0.05) and QRS intervals.③ AZM 41.5 mg·L-1 did not significantly change the action potential amplitude (APA),action potential durations at 50％ (APD50) and 90％ (APD90) repolarization levels,or L-type Ca2+ and Na+ currents.However,AZM+SM 5 mg· L-1 significantly reduced APA (P＜0.05),shortened APD50 (P＜0.05) and APD90 (P＜0.05) and inhibited the L-type Ca2+ (P＜0.05) and Na+ (P＜0.05) currents.CONCLUSION AZM and SM has potential prorrhythmic risks.The combined use might cause higher risk of arrhythmia.The underlying mechanism for proarrhythmia is mediated by inhibition of the L-type Ca2+ and Na+ currents.
RESUMEN
OBJECTIVE To explore kinetic features and its underlying mechanism of the positive inotropic effect of liguzinediol(LZDO)in rats. METHODS ①An In vivo study was made to record the effect of LZDO 20 mg · kg-1 injected for 30 consecutive min from the left external jugular vein on pressure-volume relationships. ②Ex vivo study was used to record the antagonistic effect of LZDO on reduced contractility induced by caffeine. Caffeine and LZDO were perfused as follows:normal perfusion solution, caffeine 0.5 mmol · L-1,and then caffeine 0.5 mmol · L-1+LZDO 100 μmol · L-1. ③ Ca2+ transient from cardiomyocyte sarcoplasmic reticulum (SR) was measured to analyze the effect of LZDO on Ca2 +release blocked by thapsigargin. Thapsigargin and LZDO were perfused as follows:normal perfusion solution,thapsigargin 2 μmol · L-1,and then thapsigargin 2 μmol · L-1+LZDO 100 μmol · L-1.④The SR vesicles were prepared and the effect of LZDO(1,10 and 100μmol·L-1)on sarcoplasmic reticulum Ca2+ATPase(SERCA2a)activity was determined according to the ultramicro-Ca2+-ATP enzyme kit. RESULTS ① LZDO 20 mg · kg- 1 significantly reduced the end-systolic volume (Ves) and enhanced the end-systolic pressure (Pes),stroke volume (SV),ejection fraction (EF),cardiac output(CO),peak rate of rise of left ventricular pressure(+dp/dtmax)and stroke work(SW)(P<0.05). However,LZDO 20 mg · kg-1 did not significantly change the heart rate(HR )or the end-diastolic volume (Ved). ② Caffeine 0.5 mmol · L- 1 significantly enhanced HR,left ventricular developed pressure (LVDP ),and+dp∶dtmax at 5 min after caffeine and decreased at 30 min. However,LZDO 100μmol·L-1 restored the reduced HR,LVDP,and+dp/dtmax induced by caffeine at 30 min(P<0.05).③Thapsigargin 2μmol·L-1 significantly reduced the SR Ca2+transient from perfusion solution group(100±5)%to(51± 5)%(P<0.05) and LZDO 100 μmol · L-1 failed to restore the decreased Ca2+ transient〔(49 ± 4)%〕. Normalized Ca2+transients were reduced by thapsigargin 2μmol·L-1 and thapsigargin 2μmol·L-1+LZDO 100 μmol · L-1. ④ LZDO(10 and 100 μmol · L-1)significantly increased the activities of SERCA2a in perfusion solution group 0.98±0.10 to 1.17±0.20 and (1.43±0.09)μmol Pi·g-1·h-1,respectively(P<0.05). CONCLUSION LZDO can enhance SR Ca2+ gradient by activating the SERCA2a and might be developed to serve as a potential positive inotropic agent in clinical settings.