Fogarty K E, Kidd J F, Tuft R A, Thorn P
Biomedical Imaging Group, Department of Physiology, University of Massachusetts Medical School, Worcester, Massachusetts 01650 USA.
Biophys J. 2000 May;78(5):2298-306. doi: 10.1016/S0006-3495(00)76776-2.
InsP(3)-evoked elementary Ca(2+) release events have been postulated to play a role in providing the building blocks of larger Ca(2+) signals. In pancreatic acinar cells, low concentrations of acetylcholine or the injection of low concentrations of InsP(3) elicit a train of spatially localized Ca(2+) spikes. In this study we have quantified these responses and compared the Ca(2+) signals to the elementary events shown in Xenopus oocytes. The results demonstrate, at the same concentrations of InsP(3), Ca(2+) signals consisting of one population of small transient Ca(2+) release events and a second distinct population of larger Ca(2+) spikes. The signal mass amplitudes of both types of events are within the range of amplitudes for the elementary events in Xenopus oocytes. However, the bimodal Ca(2+) distribution of Ca(2+) responses we observe is not consistent with the continuum of event sizes seen in Xenopus. We conclude that the two types of InsP(3)-dependent events in acinar cells are both elementary Ca(2+) signals, which are independent of one another. Our data indicate a complexity to the organization of the Ca(2+) release apparatus in acinar cells, which might result from the presence of multiple InsP(3) receptor isoforms, and is likely to be important in the physiology of these cells.
三磷酸肌醇（InsP(3)）诱发的基本钙离子（Ca(2+)）释放事件被认为在提供更大钙离子信号的构建单元方面发挥作用。在胰腺腺泡细胞中，低浓度的乙酰胆碱或注射低浓度的三磷酸肌醇会引发一系列空间局部化的钙离子尖峰。在本研究中，我们对这些反应进行了量化，并将钙离子信号与非洲爪蟾卵母细胞中显示的基本事件进行了比较。结果表明，在相同浓度的三磷酸肌醇下，钙离子信号由一群小的瞬时钙离子释放事件和另一群明显不同的较大钙离子尖峰组成。这两种类型事件的信号质量幅度都在非洲爪蟾卵母细胞基本事件的幅度范围内。然而，我们观察到的钙离子反应的双峰钙离子分布与非洲爪蟾中看到的事件大小的连续体不一致。我们得出结论，腺泡细胞中两种类型的三磷酸肌醇依赖性事件都是基本的钙离子信号，它们彼此独立。我们的数据表明腺泡细胞中钙离子释放装置的组织具有复杂性，这可能是由于多种三磷酸肌醇受体亚型的存在导致的，并且可能在这些细胞的生理学中很重要。
