CAJ | 학술논문

应用全细胞膜片钳技术,研究了M胆碱能对不同孕期的胚胎小鼠心肌细胞的起搏电流(If)的调节.我们发现,在胚胎发育的早期阶段,M胆碱能受体激动剂(muscarinic agonist carbachol,CCh)明显抑制If,但在胚胎发育的晚期阶段,CCh对If的抑制作用消失.腺苷酸环化酶(adeinylate cyclase,AC)激动剂毛喉素Forskolin和非选择性磷酸二酯酶(PDE)抑制剂IBMX均可增强发育早期阶段和晚期阶段的If.但有趣的是,尽管Forskolin和IBMX可增加基础If,它们对CCh抑制的If的作用却大不相同.在胚胎发育的早期阶段,Forskolin不能拮抗CCh对If的抑制作用,但IBMX可以.在发育的中期阶段Forskolin可以拮抗CCh的抑制作用,但IBMX不可以.因此,我们推断,CCh可能是通过调控细胞内的cAMP水平来调节If的.但是在胚胎发育的早期阶段和中期阶段,CCh可能通过不同的信号转导通路来实现对胞内cAMP的水平调控.在发育的早期阶段,CCh主要是通过增强PDE的活性,加速cAMP的降解而实现对If的调控.而在发育的中期阶段,CCh则主要通过与AC耦联,抑制其活性,通过减慢cAMP的合成而实现对If的调控.
응용전세포막편겸기술,연구료M담감능대불동잉기적배태소서심기세포적기박전류(If)적조절.아문발현,재배태발육적조기계단,M담감능수체격동제(muscarinic agonist carbachol,CCh)명현억제If,단재배태발육적만기계단,CCh대If적억제작용소실.선감산배화매(adeinylate cyclase,AC)격동제모후소Forskolin화비선택성린산이지매(PDE)억제제IBMX균가증강발육조기계단화만기계단적If.단유취적시,진관Forskolin화IBMX가증가기출If,타문대CCh억제적If적작용각대불상동.재배태발육적조기계단,Forskolin불능길항CCh대If적억제작용,단IBMX가이.재발육적중기계단Forskolin가이길항CCh적억제작용,단IBMX불가이.인차,아문추단,CCh가능시통과조공세포내적cAMP수평래조절If적.단시재배태발육적조기계단화중기계단,CCh가능통과불동적신호전도통로래실현대포내cAMP적수평조공.재발육적조기계단,CCh주요시통과증강PDE적활성,가속cAMP적강해이실현대If적조공.이재발육적중기계단,CCh칙주요통과여AC우련,억제기활성,통과감만cAMP적합성이실현대If적조공.
We isolated mouse embryonic cardiomyocytes derived from timed-pregnant females at different periods and used patchclamp technique to investigate the muscarinic cholinergic modulation of pacemaker current If in different developmental stages. In early development stage (EDS), muscarinic agonist carbachol (CCh) significantly decreased the magnitude of the pacemaker current If but had no effect in late development stage (LDS). Forskolin (a direct adenylate cyclase activator) and IBMX (a non-selective phosphodiesterase inhibitor) increased If in both EDS and LDS cells. Interestingly, although both forskolin and IBMX increased basal If, their effects on CCh-inhibited If were different. Forskolin did not reverse the inhibitory action of CCh until intermediate development stage (IDS). In contrast, IBMX reversed the inhibitory action of CCh on If in EDS but not in IDS. It is suggested that a decrease in intracellular cAMP is a possible mechanism for CCh to modulate If. During the EDS and IDS CCh controls the cytoplasmic cAMP level by different pathways: In EDS, CCh modulates If possibly by activating PDE which accelerates the breakdown of cAMP, but in IDS possibly by inhibiting adenylate cyclase (AC) which then reduces the synthesis of cAMP.