The Making Of Diabetic Guinea Pigs By Streptozotocin And The Effect Of Extracellular Fluid Vairous Of K Concentration On The Action Potentials In Papillary Muscle Of Guinea Pig And Its Underlying Mechanism

Diabeties,a common etabolized disease, induce arrhythmia， cardiachypertrophy，heart failure，which is related to Potassium channels remodeled.Heart rate-corrected QT interval and action potential duration were prolongedby20%in a rabbit model of alloxan-induced diabetes.Several K⁺currentswere found decreased in diabetic rabbits including rapid delayed redtifier Kcurrent(I_kr) and slow delayed redtifier K current(I_ks) reduced.,I_krand I_ksmainlyrepolariztion currents,which were encoded by the HERG and theKCNQ1,KCNE1. The aim of the study was to investigate the effects ofvairous of K concentration on the action potential in multicellular preparationsincluding papillary muscle and STZ-induced diabetic guinea pig on the actionpotential and study its underlying mechanism.Part1Established diabetic model of guinea pig.Aim: To establish the model of diabetic guinea pig.Methods: Male guinea pigs weighting250-350g were raised for1weekbefore experiment.20guinea pigs were divided into two groups at random,that is control group and model group. Each group has10animals. All ofanimals were starved for12hours before experiment. Diabetes was inducedby a single rapidly intravenous injection of sterptozotocin （STZ,200mg/kg,Solarbio）. The control group were treated with a single intravenous injectionof citrate buffer. Measured body weight and concentration of plasma glucoseat Days0,2,7,14after injection of streptozotocin or buffer in control groupand model group. The pancreas were taken out after14days injected STZ.HE stained were done to observe pathologically under the optical microscope.The conventional glass electrode technique was used to record the action potential of papillary muscle from control or model guinea pig. The real-timePCR method was employed to measure ERG and KCNQ1RNA ofmyocardium from control or model guinea pig.Results:（1） The STZ-induced guinea pig showed fur dark, marasmus,polydipsia, polyuria. During experiment, four of model group died. All of thecontrol animals were survival and normal. Compared with the control group,the body weight of the model group reduced significantly after2,7,14days ofinjection （p<0.01）.（2） Compared with control group （6.4±0.6mmol/L），theplasma glucose concentration of the model group （17.4±1.4mmol/L）increased significantly after2days of injection.（3） The pancreatic islet cell ofthe model group is damaged, the number of pancreatic cell decrease andglomerular arterioles also occur.（4） Compared with the control group（102±12ms）, the APD30（84±8ms）of the model group reduced significantly（p<0.05）;Compared with the control group（206±6ms）, the APD₉₀（168±2ms）of the model group reduced significantly （p<0.01）;Compared with thecontrol group（104±11ms）, the APD_90-30（84±6ms）of the model groupreduced significantly （p<0.01）; Compared with the control group（20±2v/s）,the Vmax（16±1v/s）of the model group reduced significantly （p<0.01）.（5）Compared with the control group, the ERG DNA（19.63±0.66）of the modelgroup （5.29±0.1） reduced significantly（p<0.01）; Compared with the controlgroup, the KCNQ1RNA（19.63±0.66）of the model group （1.17±0.05）increased significantly（p<0.01）.Conclusion: In STZ-induced group was the boday weightingsignificantly higher than in the control group on Days14; but the plasmaglucose concentration higher in the control group only on Days2.Part2The effect of various of K⁺concentration on the action potential ofpapillary muscle in guinea pig and its underlying mechanismAim:The effect of various of K⁺concentration on the action potential ofpapillary muscle in control and STZ-induced guinea pig and its underlyingmechanism.Methods: The action potential profile was collected before and30min later in the presence of various of K⁺concentration on the action potential ofpapillary muscle in control and STZ-induced guinea pig under1Hzstimulation frequency. The following action potential parameters werecalculated by using a self-edited software: action potential altitude （APA）,maximal rate of0phase depolarization （Vmax）, duration of30%depolarization（APD30）, duration of90%depolarization (APD₉₀) and duration of90%depolarization (APD₉₀) minus duration of30%depolarization （APD30）(APD₉₀-APD30).Results:（1）1mM K⁺influenced AP of papillary muscle in control group:Compared with the normal Tyrode solution The APD30（107±5ms） at thestimulatory frequencies of1Hz were respectively shorted in the presence of1mM K⁺the APD30（91±4ms）（P<0.01）; Compared with the normal Tyrodesolution The APD₉₀（191±6ms） at the stimulatory frequencies of1Hz wererespectively pronged in the presence of1mM K⁺the APD₉₀（246±18ms）（P<0.01）;Compared with the normal Tyrode solution The APD_90-30（86±5ms）at the stimulatory frequencies of1Hz were respectively pronged in thepresence of1Mm K the APD_90-30（155±16ms）（P<0.01）, meanwhile VmaxandAPA no change （P>0.05）.（2）1mM K⁺influenced AP of papillary muscle inmodel group: Compared with the normal Tyrode solution The APD₉₀（164±8ms） at the stimulatory frequencies of1Hz were respectively pronged in thepresence of1mM K⁺the APD₉₀（224±14ms）（P<0.01）;Compared with thenormal Tyrode solution The APD_90-30（68±6ms） at the stimulatory frequenciesof1Hz were respectively pronged in the presence of1Mm K the APD_90-30（121±25ms）（P<0.01）, meanwhile Vmax, APD₉₀and APA no change （P>0.05）,accompanied with EAD and triggered activity.（3）10mM K⁺influenced AP ofpapillary muscle in control group: Compared with the normal Tyrode solutionThe APD30（100±9ms） at the stimulatory frequencies of1Hz wererespectively shorted in the presence of10mM K⁺the APD30（69±12ms）（P<0.01）; Compared with the normal Tyrode solution The APD₉₀（200±8ms）at the stimulatory frequencies of1Hz were respectively shorted in thepresence of10mM K⁺the APD₉₀（141±10ms）（P<0.01）;Compared with the normal Tyrode solution The APD_90-30（110±12ms） at the stimulatoryfrequencies of1Hz were respectively shorted in the presence of10mM K⁺the APD_90-30（68±4ms）（P<0.01）; Compared with the normal Tyrode solutionThe APA（126±7mV） at the stimulatory frequencies of1Hz were respectivelydecreased in the presence of10mM K⁺the APA （109±5mV）（P<0.01）,meanwhile Vmaxno change （P>0.05）.（4）10mM K⁺influenced AP of papillarymuscle in model group: Compared with the normal Tyrode solution TheAPD₉₀（176±6ms）, APD_90-30（84±7ms）at the stimulatory frequencies of1Hzwere respectively shorted in the presence of10mM K⁺the APD₉₀（148±11ms）APD_90-30（70±5ms）（P<0.01）; meanwhile APA, APD30and Vmaxno change（P>0.05）.（5）)30mM K⁺influenced AP of papillary muscle in control group:Compared with the normal Tyrode solution The APA（126±3mV）, APD30（100±3ms）, APD₉₀（198±3ms）, APD_90-30（98±3ms）, Vmax（28±1v/s） at thestimulatory frequencies of1Hz were respectively shorted in the presence of30mM K⁺The APA（91±2mV）, APD30（58±2ms）, APD₉₀（106±5ms）,APD_90-30（98±3ms）, Vmax（18±1v/s）;（P<0.01）.（6）30mM K⁺influenced APof papillary muscle in model group: Compared with the normal Tyrodesolution The APA（113±4mV）, APD30（80±4ms）, APD₉₀（176±6ms）,APD_90-30（84±7ms）, Vmax（26±6v/s） at the stimulatory frequencies of1Hzwere respectively shorted in the presence of30mM K⁺The APA（109±7mV）,APD30（77±10ms）, APD₉₀（148±11ms）, APD_90-30（71±5ms）, Vmax（22±7v/s）;（P<0.01）.（7） Compared with control group,the mRNA expression levelsof the HERG and the KCNQ1,KCNE1were significantly up-regulated inboth DM group and DM+1mM K⁺group.Compared with DM groupthemRNA expression levels of the HERG(control（19.6±0.7）, DM（5.29±0.2）,DM+1mM K⁺（1.35±0.04） and the KCNQ1(control（3.48±0.08）, DM（1.17±0.05）, DM+1mMK⁺（0.65±0.04）, were significantly up-regulated in DM+1mM K⁺group （P<0.01）.Conclusion:1.extracellular K⁺concentration effect ADPs of controlgroup and model group. Reduction of [K⁺]o（1mM） led to prong APD ofcontrol and DM group, but high [K⁺]o（10mM） were opposite.（2） On the contrary, degradation of APDs in the STZ-induced group,I_krand I_kswereincreased on the condition of the DM group and reduction of [K⁺]o（1mM）.Part3The effect of high concentration of glucose on the action potentialof papillary muscle in guinea pig and its underlying mechanismAim:The effect of high concentration of glucose on the action potentialof papillary muscle in control and STZ-induced guinea pig and its underlyingmechanism.Methods: The action potential profile was collected before and30minlater in the presence of100mM glucose concentration on the action potentialof papillary muscle in control and STZ-induced guinea pig under1Hzstimulation frequency. The following action potential parameters werecalculated by using a self-edited software: action potential altitude （APA）,maximal rate of0phase depolarization （Vmax）, duration of30%depolarization（APD30）, duration of90%depolarization (APD₉₀) and duration of90%depolarization (APD₉₀) minus duration of30%depolarization （APD30）(APD₉₀-APD30).Results:（1）100mM Glucose influenced AP of papillary muscle incontrol group: Compared with the normal Tyrode solution The APD30（120±6ms）, APD₉₀（209±9ms）, at the stimulatory frequencies of1Hz wererespectively shorted in the presence of100mM Glucose the APD30（110±7ms）,APD₉₀（197±5ms）（P<0.05）, meanwhile Vmax, APA, APD_90-30no change（P>0.05）.（2）100mM Glucose influenced AP of papillary muscle in modelgroup: Compared with the normal Tyrode solution The APD₉₀（166±4ms）, atthe stimulatory frequencies of1Hz were respectively shorted in the presenceof100mM Glucose the APD₉₀（152±5ms）（P<0.01）, meanwhile Vmax, APA,APD30, APD_90-30no change （P>0.05）.Conclusion: The APD₉₀on control group and STZ-induced group at thestimulatory frequencies of1Hz were shorted in the presence of100mMglucose.