Cajal间质细胞与胃肠起搏

Interstitial cells of cajal and gastrointestinal pacemakeing

近年的研究发现,Cajal间质细胞(ICC)是胃肠起博细胞。ICC呈星状,有长的突起。均表达c-kit,ICC之间、ICC与周围平滑肌形成缝隙连接,可自发产生起博电位。ICC起博的机制可能是:ICC自发产生的单元电位总和达阈值,激活电压依赖的Ca2+可通透的离子通道,形成起博电位的初始部分;Ca2+内流,激活对细胞内Ca2+敏感的酶,使IP3生成增加;从而增高IP3的浓度,引起Ca2+从内源性Ca2+库瞬间释放,使细胞内Ca2+浓度上升,活化细胞膜上Ca2+活化的Cl-通道,细胞膜去极化产生平台部分;Ca2+的进入使局部Ca2+浓度上升,通道失活,起搏电位终止。

It has recently become apparent that interstitial cells of Cajal （ICC） is the pacemaker cells of gastrointestine. ICC are stellate-shaped cells with long process. ICC express c-kit and form gap junctional connection with each other and with surrounding smooth muscle cells. Isolated ICC are found to spontaneously generate pacemaker potential. The following mechanisms are considered to be involved in the generation of pacemaker potential. Depolarization of the membrane by summation of unitary potentials may activate voltage-dependent Ca^2＋ -permeable channels to form the primary component of the pacemaker potentials. Ca^2＋ influx through voltage-dependent Ca^2＋ -permeable channels activates Ca^2＋ -sensitive enzymes such as phospholipase C and enchances the production of IP3. IP3 induces an instantaneous release of Ca^2＋ from internal stores, and the elevated cytosolic Ca^2＋ concentration, which activates Ca^2＋ -activated CI channels in the plasma membrane to depolarize the membrane and form the plateau component. With the Ca^2＋ entering, the local concentration of Ca^2＋ rise and the channels are inactivated, so terminating the pacemaker potential.