Effects Of Pentamethylquercetin On Contractile Force And Electrophysiological Characteristics Of Cardiac Muscle In Guinea Pig

Phytopolyphenol of flavonoids have always been highly concerned in the medicine kingdom. Quercetin (QUE) is one of the flavonoids which have been very well researched. It is confirmed that they have a variety of biological activities, including anti-oxidation, inhibition of platelet aggregation, free radical scavenging, anti- inflammatory, blood pressure reduction, vasodilatation, protection of endothelium and so on. However, they have a low bioavailability, short half life and low potency, which hampered their exploitation and utilization.Polymethoxylflavonoids are the methylation derivates of polyphenolflavonoid, which have obvious pharmacokinetics characteristics and pharmacodynamics advantage. However, there is no breakthrough in the extraction technology of natural polymath- oxylfavonoids up to now. The yield of natural polymethoxylflavonoids is limited and the price is very high, which hindered the research. So we synthesized pentamethyl- quercetin (PMQ) that is high purity and low price. In this study, the effects of PMQ and QUE on electrophysiological characteristics and contractile force in guinea pig cardiac muscle were investigated.PartⅠEffects of PMQ on physiological characteristics in isolated guinea pig cardiac atriaThe effects of PMQ on contractile force of left atrium and autorhythmicity in right atrium of guinea pig were investigated. PMQ produced a positive inotropic effect in isolated guinea pig left atrium. 10, 30, 100μmol·L-1 PMQ increased the contractile force by 9±3%, 24±7% and 29±12%, respectively. 10, 30, 100μmol·L-1 QUE increased the contractile force by 12±2%, 15±3%, and 32±9%, respectively. PMQ had no obvious effects on autorhythmicity of right atrium. 10, 30, 100μmol·L-1 QUE produced a positive chronotropic action by 8±1%, 15±2%, 24±2%, respectively. 0.1% DMSO has no obvious effects on above parameters. PartⅡEffects of PMQ on the action potential and contractile force in guinea pig papillary musclesAction potentials and contractile force in isolated papillary muscle of guinea pig were simultaneously examined. 10, 30μmol·L-1 QUE increased the contractile force and prolonged APD20, APD50, APD90 (n=8, P<0.01). 30, 100μmol·L-1 PMQ increased the contractile force by 13±3% and 24±6 %( n=7, P<0.01) respectively, but had no obvious effects on APD. No change of the RP and APA were observed in PMQ and QUE groups.PartⅢEffects of PMQ on ICa.L and IK1 in guinea pig ventricular myocytes1. Effects of PMQ on ICa.L in guinea pig ventricular myocytes Guinea pig ventricular myocytes were isolated enzymatically and whole cell patch clamp technique was used to record ICa.L. 10, 30μmol·L-1 QUE decreased peak ICa.L by 12±3 %( n=8, P<0.01) and 18±5 %( n=6, P<0.05). V1/2 and K were changed from -11.1±0.60 mV and 5.61±0.23 to -18.7±1.00 mV and 4.90±0.37 respectively in the present of 10μmol·L-1 QUE (P<0.05). V1/2 and K were -11.9±0.78 mV and 6.30±0.24 for control and -21.4±0.51 mV (P<0.01) and 6.21±0.43 (P>0.05) in 30μmol·L-1 QUE.10μmol·L-1 PMQ had no effects on L-type calcium current. 30μmol·L-1 PMQ decreased peak L-type cacium current by 20±3 %( n=7, P<0.01), and this effects were partially reversed by washout. The maximal activating voltage of ICa.L was not changed. For activation, V1/2 and K were -13.28±1.72mV and 5.55±0.2 for control and -14.29±2.04 mV and 5.40±0.56 in the present of 30μmol·L-1 PMQ (P>0.05).2. Effects of PMQ on IK1 in guinea pig ventricular myocytesThe effects of PMQ and QUE on IK1 in guinea pig ventricular myocytes were assessed by whole cell patch clamp techniques. 10, 30μmol·L-1 QUE inhibited IK1 by 25±6 %( n=6, P<0.01) and 37±4 %( n=6, P<0.01) respectively. 10μmol·L-1 PMQ had no obvious effects on IK1. 30μmol·L-1 PMQ inhibited IK1 by 18±2 %( n=7, P<0.01).PartⅣEffects of PMQ on introcelluar free calcium concentration of guinea pig ventricular myocytesIntracellucar free calcium concentration ([Ca2+]i) of guinea pig ventricular myocytes were measured by Confocal Laser Microscopy techniques. 1μmol·L-1 PMQ had on obvious effects on [Ca2+]i, 3, 30μmol·L-1 PMQ increased the [Ca2+]i by 72±16%,122±24%(n=7,P<0.01).In conclusion:1. Both PMQ and QUE produced positive inotropic effect of left atrium significantly. PMQ had no obvious effects on autorhythmicity of right atrium but QUE produced a positive chronotropic action.2. PMQ had no obvious effects on action potential in guinea pig papillary muscles; QUE prolonged the action potential duration. Both PMQ and QUE produced positive inotropic effect in guinea pig papillary muscles.3. PMQ decreased ICa.L and IK1 in guinea pig ventricular myocytes, but the potent is much weaker than QUE.4. PMQ increased the intracellular free calcium of guinea pig ventricular myocytes.