ABSTRACT
Aim To explore the arrhythmic risk of Chan Su intravenous injection(CS)and its underlying mechanismin in the absent or presence of IL-6.Methods The recording techniques of guinea pig in vivo ECG, the action potential, L-type Ca2+ and Na+ currents from left ventricular myocytes were used to analyze heart rate(HR), P-R, QRS and QTc intervals and the underlying mechanism.Results① CS at one time CRD(clinically relevant dose)insignificantly changed the guinea pig in vivo ECG.However, the IL-6(18.4 μg·kg-1)only and the combinational use of IL-6(18.4 μg·kg-1)plus CS(one time CRD)remarkably prolonged the P-R and QTc intervals.② The CS at one time CRC(clinically relevant concentration)had no significant change in the action potential duration at 90% repolarization level(APD90).The IL-6(20 μg·L-1)only and the combination of CS at one time CRC plus IL-6(20 μg·L-1)significantly prolonged APD90.③ Moreover, the IL-6(20 μg·L-1)combined with CS at one time CRC significantly inhibited the L-type Ca2+ current. CS at one, five, ten time CRC, IL-6(20 μg·L-1)alone and IL-6(20 μg·L-1)combined with CS had no significant effects on Na+current.Conclusions CS intravenous injection has low risk of arrhythmia in the clinical settings.However, in presence of high titer of IL-6 characterized by inflammation, CS may induce the atrioventricular conduction block due to the blockade effect on Ca2+ current by both of CS and IL-6.
ABSTRACT
Aim To investigate the inotropic effect of PF-04957325, a phosphodiesterase type 8 inhibitor, in normal rats and its underlying molecular mechanism. Methods The techniques of in vivo rat left ventricular pressure-volume loop (P-V loop) and isolated perfusion rat heart were used to analyze the hemodynamics and positive inotropic effect of rat hearts. The Ca transient induced by field stimulation was used to analyze the hemodynamics of sarcoplasmic reticulum (SR) Ca + uptaking. Western blot was used to analyze the phosphorylation levels of SR phospolamban (PLB) and ryanodine receptor type 2 (RyR2). Results The P-V loop experiment indicated that PF-04957325 (0.5 mg · kg