A Role of c-kit tyrosinekinase of physiological development of the gastrointestinal pacemaker activity

关于胃肠道电和机械节律的起源，一类特化细胞，通常被称为间质细胞（IC），被认为是起搏器细胞。然而，由于胃肠道肌肉和IC网络的结构复杂性，IC的功能很难在完整肌肉中研究。我们采用了一种不同的方法来探索肠内ic的功能。结果表明：1)小鼠发育中的胃肠道平滑肌层中有一类细胞表达Kit-基因，该基因是编码PDGF/CSF-I受体家族中酪氨酸受体的原癌基因，在出生后几天内体外注射原癌基因产物Kit蛋白的中和抗体（ACK2）可减少表达Kit的细胞数量；2) ACK2特异性地标记了小鼠胃肠道中更多的内脏细胞（ICs）， ACK2处理诱导了电慢波活动的丧失和平滑肌细胞膜的去极化。3)我们成功地在小鼠小肠原代培养中分离了ic，并记录了这些原代培养的ic自发活动电流。4)在所有c-kit ^+细胞中均未观察到电压敏感的Na^+和Ca^<2+>电流，但在电流箝位条件下观察到膜电压的节律波动，其中只有Cl^-渗透。5)在出生当天（第0天）未显示任何自发收缩活动的新生儿回肠中，ACh （>0 ^<-8>M）诱导了剂量相关的持续收缩，但对照小鼠对ACh的收缩反应在出生后每天敏感性下降，而ack2处理的动物回肠对ACh以及前列腺素E1和F2a的敏感性未显示下降。这些观察结果表明，kit-信号通路在肠道起搏器细胞ic的发育中起着重要作用。IC网络发育障碍不仅会影响胃肠道运动，还会影响回肠平滑肌的药理特性。少

As to origin of electrical and mechanical rhythmicity in the gastrointestinal tract, a class of specialized cells, often referred to as interstitial cells (IC) have been suggested to serve as pacemaker cells However, the function of ICs has been difficult to investigate in intact muscles because of the structural complexities of GI muscle and the IC network. We took a different approach to explore function of the ICs in the intestine. Results are as follows, 1) A certain type of cells in smooth muscle layrs of developing gastrointestinal tract in the mouse expresses Kit-gene which is a proto-oncogene encoding a receptor tyrosine in PDGF/CSF-I receptor family and in vitro injection of a neutralizing antibody (ACK2) for the proto-oncogene product, Kit protein, during the first few days after birth reduced the number of the Kit-expressing cells, which was accompanied by impairment of development of normal rhythmic mechanical activity in the mouse intestine, 2) ACK2 specifically labels int … More erstitial cells (ICs) in the mouse GI tracts, and ACK2-treatment induces a loss of electrical slow wave activity and depolarization of the membranes of smooth muscle cells, 3) we have succeeded in isolating ICs in primary culture of the mice small intestine and recorded spontaneously active electrical currents from these primary cultured ICs, 4) Both of the voltage-sensitive Na^+ and Ca^<2+> currents were not observed clearly in the all c-kit ^+ cells tested, but the rhythmic fluctuation of membrane voltage was observed under the current-clamp condition, where only Cl^- permeates, 5) In the ileum of neonates on the day of birth (day 0 pp) which did not show any spontaneous contractile activity, ACh (>10^<-8>M) induced a dose-related sustained contraction, but the contractile responses to ACh declined in sensitivity each day after birth in the control mice, while ileum of ACK2-treated animals did not show a decrease in the sensitivity to ACh as well as prostaglandin E1 and F2a. These observations indicate that the kit--signaling pathway is important in the development of ICs as pacemaker cells in the intestinal tract. Impairment of development of the IC network would not only affect GI motility but also affect pharmacological characteristics of the ileac smooth muscle. Less