Putney J W, Burgess G M, Halenda S P, McKinney J S, Rubin R P
Biochem J. 1983 May 15;212(2):483-8. doi: 10.1042/bj2120483.
Experiments were carried out to assess the effects of secretagogues on the polyphosphoinositides phosphatidylinositol 4-phosphate (PtdIns4P) and phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] on preparations of exocrine pancreas in vitro. Carbachol and caerulein provoked a rapid (less than 1 min) breakdown of 15-20% of [32P]PtdIns(4,5)P2 in isolated pancreatic acini, but did not affect [32P]PtdIns4P. In contrast, the Ca2+ ionophore ionomycin had no immediate effect on the levels of either inositide but caused a parallel fall in both lipids after 5-10 min. A similar decrease in [32P]PtdIns(4,5)P2 due to carbachol was obtained with isolated acini and isolated cells, despite the fact that the secretory response of isolated cells was considerably less than that of isolated acini. Loss of [32P]PtdIns(4,5)P2 elicited by carbachol or caerulein was unaffected either by the addition of EGTA in excess of extracellular Ca2+ or when a protocol was employed that eliminated caerulein-induced intracellular Ca2+-release. These results suggest that agonist-induced PtdIns(4,5)P2 breakdown in the exocrine pancreas may be an early step in the stimulus-response coupling pathway and also suggest that this breakdown is not dependent on Ca2+-mobilization.
开展实验以评估促分泌素对外分泌胰腺体外制剂中多磷酸肌醇磷脂酰肌醇4 - 磷酸（PtdIns4P）和磷脂酰肌醇4,5 - 二磷酸[PtdIns(4,5)P2]的影响。卡巴胆碱和蛙皮素可使分离的胰腺腺泡中15 - 20%的[32P]PtdIns(4,5)P2迅速（不到1分钟）分解，但不影响[32P]PtdIns4P。相反，Ca2+离子载体离子霉素对两种肌醇磷脂的水平无直接影响，但5 - 10分钟后两种脂质平行下降。尽管分离细胞的分泌反应远低于分离腺泡，但卡巴胆碱引起的[32P]PtdIns(4,5)P2减少在分离腺泡和分离细胞中均有出现。卡巴胆碱或蛙皮素引起的[32P]PtdIns(4,5)P2丢失，在加入过量细胞外Ca2+的EGTA时或采用消除蛙皮素诱导的细胞内Ca2+释放的方案时均不受影响。这些结果表明，激动剂诱导的外分泌胰腺中PtdIns(4,5)P2分解可能是刺激 - 反应偶联途径中的早期步骤，也表明这种分解不依赖于Ca2+动员。
