Role of cyclic ADP-ribose in signal transduction in airway cells.

本实验研究了气管黏膜下腺泡细胞和气管平滑肌细胞的基本电生理特性。此外，一些新发现的钙动员第二信使环ADP-核糖在这些细胞中的作用进行了研究。主要研究结果如下：1.气道腺体通过胞内释放的Ca^2+分泌电解质.肌醇1，4，5-三磷酸（IP_3）在Cl^--分泌中起重要作用。然而，即使在灌注IP_3受体单克隆抗体的细胞中，ACh也能引起Ca^<2+>依赖的K电流。胞内注射cADPR可引起腺细胞外向K电流.气管腺微粒体部分对cADPR有释放Ca^<2+>的反应，IP_3脱敏后的微粒体也对cADPR有反应，提示cADPR相关的Ca（2+）释放过程中有分离的Ca^<2+-库参与. cADPR不影响离体斑片中K通道的活性，也不影响外界Ca^2+的内流。用RT-PCR检测到CD 38-mRNA在腺细胞中表达，而在气管平滑肌细胞中未检测到。这些发现表明，在气道腺细胞中存在cADPR途径的Ca^<2+>动员。

We investigated the basic electrophysiological characteristics of airway cells including tracheal submucosal gland acinar cells and tracheal smooth muscle. In addition, some roles of newly identified calcium mobilizing second messenger cyclic ADP-ribose was studied in these cells. Main findings of this project were as follows.1. Airway glands secrete electrolytes through Ca^<2+> released intracellularly. Inositol 1,4,5-trisphosphate (IP_3) plays a crucial role in Cl^--secretion. However, even in the cells perfused with mAb to IP_3 receptor, ACh caused a Ca^<2+>-dependent K-current.2. Intrcellular injection of cADPR caused outward K-current in gland cells.3. Microsomal fraction derived from tracheal gland released Ca^<2+> in respond to cADPR.Microsomes desensitized with IP_3 also responded to cADPR suggesting a separated Ca^<2+>-store is involved in cADPR-associated Ca(2+) release.4. cADPR did not affect the K-channel activities in excised patches nor affected influx of outside Ca^<2+>.5. Using RT-PCR,CD38-mRNA was detected in gland cells but not in tracheal smooth muscle cells. These findings suggest an existence of cADPR-pathways in Ca^<2+>-mobilization in airway gland cells.