A study of exocrine cell functions using local photolysis of caged compounds.

激动剂在外分泌腺泡细胞的触发区引起Ca 2+ 梯度和振荡。使用低亲和力的Ca^2指示剂染料BTC，我们发现激动剂将触发区的Ca^2浓度提高至10μM。与用fura-2获得的结果比较表明在触发区有大量的Ca ^ 2 释放和Ca ^ 2 结构域。所得的微摩尔Ca 2+ 梯度对于通过电容测量研究的酶原颗粒的胞吐作用是必要且充分的。相反，亚微摩尔Ca 2+ 梯度选择性地引起管腔和基础离子通道的连续激活。这些结果强调了微摩尔Ca^2梯度在胞吐作用中的关键作用，并提示使用低亲和力Ca^2指示剂重新研究其他细胞。

Agonists evoke Ca^<2+> gradients and oscillations initiating at the trigger zone in exocrine acinar cells. Using a low affinity Ca^<2+> indicator dye, BTC,we found that agonists raised Ca^<2+> concentration as high as 10 muM at the trigger zone. Comparison with the results obtained with fura-2 suggests profuse Ca^<2+> release and Ca^<2+> domains at the trigger zone. The resulting micromolar Ca^<2+> gradients were necessary and sufficient for exocytosis of zymogen granules investigated with the capacitance measurement. In contrast, submicromolar Ca^<2+> gradients selectively gave rise to sequential activation of luminal and basal ion channels. These results emphasize critical role of the micromolar Ca^<2+> gradients in exocytosis, and prompt reinvestigation of other cells using low affinity Ca^<2+> indicators.