Graves Thomas K, Hinkle Patricia M
Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York 14642, USA.
Endocrinology. 2003 Aug;144(8):3565-74. doi: 10.1210/en.2002-0104.
The role of the Ca(2+)-induced Ca(2+) release channel (ryanodine receptor) in MIN6 pancreatic beta-cells was investigated. An endoplasmic reticulum (ER)-targeted "cameleon" was used to report lumenal free Ca(2+). Depolarization of MIN6 cells with KCl led to release of Ca(2+) from the ER. This ER Ca(2+) release was mimicked by treatment with the ryanodine receptor agonists caffeine and 4-chloro-m-cresol, reversed by voltage-gated Ca(2+) channel antagonists and blocked by treatment with antagonistic concentrations of ryanodine. The depolarization-induced rise in cytoplasmic Ca(2+) was also inhibited by ryanodine, which did not alter voltage-gated Ca(2+) channel activation. Both ER and cytoplasmic Ca(2+) changes induced by depolarization occurred in a dose-dependent manner. Glucose caused a delayed rise in cytoplasmic Ca(2+) but no detectable change in ER Ca(2+). Carbamyl choline caused ER Ca(2+) release, a response that was not altered by ryanodine. Taken together, these results provide strong evidence that Ca(2+)-induced Ca(2+) release augments cytoplasmic Ca(2+) signals in pancreatic beta-cells.
研究了Ca(2+)诱导的Ca(2+)释放通道（兰尼碱受体）在MIN6胰腺β细胞中的作用。使用内质网（ER）靶向的“cameleon”来报告内质网腔游离Ca(2+)。用氯化钾使MIN6细胞去极化导致内质网释放Ca(2+)。用兰尼碱受体激动剂咖啡因和4-氯间甲酚处理可模拟这种内质网Ca(2+)释放，电压门控Ca(2+)通道拮抗剂可使其逆转，用拮抗浓度的兰尼碱处理可将其阻断。兰尼碱也抑制了去极化诱导的细胞质Ca(2+)升高，而这并不改变电压门控Ca(2+)通道的激活。去极化诱导的内质网和细胞质Ca(2+)变化均呈剂量依赖性。葡萄糖导致细胞质Ca(2+)延迟升高，但内质网Ca(2+)无明显变化。氨甲酰胆碱导致内质网Ca(2+)释放，这种反应不受兰尼碱影响。综上所述，这些结果提供了有力证据，表明Ca(2+)诱导的Ca(2+)释放增强了胰腺β细胞中的细胞质Ca(2+)信号。
