The Effects Of Two Venoms On Ion Channels In Neonatal Rat Ventricular Myocyte

Ion channels in cardiomyocyte are the molecular basis of action potential generation and propagation as well as regulating the resting membrane potential.Thus they present important targets for drug treating heart diseases such as long/short QT syndrome.Venoms from animals contain high abundance of peptide toxins that target diverse types of ion channels and have been considered as a rich resource for developing drugs for clinic use or probes for investigating the pharmacology of ion channels.In this study,whole cell patch-clamp technique was used to explore the effects of the venoms from Selenocosmia jiafu(JF)and Buthus martensii Karsch(BmK)on the action potential and ionic currents of neonatal rat ventricular myocytes(NRVMs).We isolated cardiomyocytes from neonatal rat heart by trypsin and collagenase digestion followed by differential time attachment and medical inhibit method.The viability of cardiomyocytes after isolation reached to 90%-95%and the proportion of beating cardiomyocytes was 75%after 4 days culturing.The purity of cardiomyocytes was over 91%.Our electrophysiological data showed that JF venom at a concentration of 100?/mL significantly prolonged AP duraitons(APDs).In contrast,BmK venom shorten APDs evidently.100 ?g/mL JF venom inhibited 80%INa and 95%IKr in ventricular myocytes.In addition,the inactivation rate of IcaL was significantly reduced by venom application.However,JF venom didn't affect Ito1 and IK1 currents.Similarly,BmK venom effectively inhibited INa and ICaL,while no evident inhibitory effect on cardiac K+ channels(Ito,Iks,Ikr and Ikl)was observed.In conclusion,the pharmacological profile of venom from Selenocosmia jiafu and Buthus martensii Karsch was complex.They contain abundance of cardiac channel antagonists and might be valuable tools for investigating these ion channels as well as in developing anti-arrhythmic drugs.At present,researches of the compounds from Chansu have focused on its function of anti-tumor and analgesia.But the studies regarding to the effect of Chansu on ion channels are not enough.To explore the regulation of CS-toxicon3 31 which was extracted from Chansu on several sodium channel subtypes.Cell culture,transient transfection and whole-cell patch-clamp technique were mainly used.It was found the peak currents of Nav1.7?Nav1.3 and Nav1.4 could be inhibited by CS-toxicon331.