CAJ | 학술논문

钠钙交换是小鼠心脏发育中最早有功能性表达的通道基因.它的功能主要是通过泵出1个钙,泵入3个钠位置细胞内的钙稳态,此外可能参与兴奋收缩偶联.但是,至今钠钙交换在心脏发育过程中的功能性表达及其在细胞早期兴奋形成中的作用还不是很清楚.采用胚胎干细胞分化的心肌细胞为研究对象,发现在发育极早期,电压钳制在35 mV的条件下,10 mmol/L咖啡因诱导的内向电流的80%能被灌流液中Na+被等浓度的Li+取代(n=8).此为钠钙交换电流.所有钳制的细胞单细胞RT-PCR都检测到了NCX1亚型的mRNA表达.进一步研究了钠钙交换的功能,发现等浓度Li+取代灌流液中Na+及应用高浓度Ni2+阻断了膜电位震荡及与震荡相间的动作电位(早期膜兴奋形式).因此认为钠钙交换(NCX1亚型)在心脏发育极早期的心肌细胞中已有大量功能性表达,它对于早期自主性兴奋活动的发生起着关键性的作用.
납개교환시소서심장발육중최조유공능성표체적통도기인.타적공능주요시통과빙출1개개,빙입3개납위치세포내적개은태,차외가능삼여흥강수축우련.단시,지금납개교환재심장발육과정중적공능성표체급기재세포조기흥강형성중적작용환불시흔청초.채용배태간세포분화적심기세포위연구대상,발현재발육겁조기,전압겸제재35 mV적조건하,10 mmol/L가배인유도적내향전류적80%능피관류액중Na+피등농도적Li+취대(n=8).차위납개교환전류.소유겸제적세포단세포RT-PCR도검측도료NCX1아형적mRNA표체.진일보연구료납개교환적공능,발현등농도Li+취대관류액중Na+급응용고농도Ni2+조단료막전위진탕급여진탕상간적동작전위(조기막흥강형식).인차인위납개교환(NCX1아형)재심장발육겁조기적심기세포중이유대량공능성표체,타대우조기자주성흥강활동적발생기착관건성적작용.
Na+/Ca2+ exchanger (NCX) is the earliest functional genes in the developing mouse heart. It has been proposed to contribute to intracellular Ca2+ homeostasis and probably excitationcontraction coupling by electrogenic exchange of 1 intracellular Ca2+ ion for 3extracellular Na+ ions. To date the functional expression of NCX and its correlation with the early spontaneous electrical activity during cardiogenesis are not thoroughly clarified. Using ES cell derived cardiomyocytes, we have found at very early development stage, NCX current (INa/Ca) is the major contributor of the caffeine (10 mmol/L) induced inward current at a constant holding potential of 35 mV as isomolar Li+ replacement of external Na+ blocked nearly 80% of the evoked inward current (n=8). NCX1 mRNA was identified in all these functionally measured cardiac cells using single-cell RT-PCR. Further functional relevance was investigated. The complete abolishment of membrane fluctuations and the intercalated action potentials (the earlier patterns of spontaneous electrical activity) by isomolar Li+ replacing external Na+ and Ni2+ (5mmol/L) implicated the essentiality of NCX in the initiation of early membrane excitation. Thus we conclude that NCX1 is highly expressed even in very early stage cardiomycoytes and it plays a pivotal role in set-up of early spontaneous electrical activity.