Schermerhorn T, Sharp G W
Department of Molecular Medicine, College of Veterinary Medicine, Cornell University Ithaca, New York 14853, USA.
Cell Calcium. 2000 Mar;27(3):163-73. doi: 10.1054/ceca.2000.0107.
Norepinephrine (NE) is an inhibitor of insulin secretion that acts, in part, by decreasing intracellular free calcium ([Ca2+]i). We examined the effects of NE on [Ca2+]i in individual HIT-T15 cells loaded with indo 1. Cells were categorized as oscillators or non-oscillators on the basis of the pattern of the calcium response to glucose and the effect of NE on [Ca2+]i was subsequently measured in each cell. NE caused a simple decrease in [Ca2+]i in nonoscillators. In oscillators, NE decreased the amplitude and frequency of the oscillations. Furthermore, the duration of the NE effect in oscillators was longer than in non-oscillators. NE did not affect the rise in [Ca2+]i elicited by depolarizing concentrations of 20 mM or 35 mM KCl alone, or in the presence of 20 mM KCl, 100 microM diazoxide, and 10 mM glucose. In other experiments, NE had no effect on [Ca2+]i when the KATP channels were fully clamped with diazoxide or tolbutamide. We conclude that the action of NE to decrease [Ca2+]i in both oscillators and non-oscillators is mediated via activation of the KATP channel. Despite this common mechanism, NE exerts different effects on oscillating and non-oscillating cells.
去甲肾上腺素（NE）是胰岛素分泌的抑制剂，其部分作用是通过降低细胞内游离钙（[Ca2+]i）来实现的。我们研究了NE对加载indo 1的单个HIT-T15细胞中[Ca2+]i的影响。根据细胞对葡萄糖的钙反应模式，将细胞分为振荡细胞或非振荡细胞，随后在每个细胞中测量NE对[Ca2+]i的影响。NE使非振荡细胞中的[Ca2+]i简单降低。在振荡细胞中，NE降低了振荡的幅度和频率。此外，NE在振荡细胞中的作用持续时间比在非振荡细胞中更长。NE单独对20 mM或35 mM KCl去极化浓度引起的[Ca2+]i升高没有影响，在存在20 mM KCl、100 microM二氮嗪和10 mM葡萄糖的情况下也没有影响。在其他实验中，当KATP通道用二氮嗪或甲苯磺丁脲完全钳制时，NE对[Ca2+]i没有影响。我们得出结论，NE在振荡细胞和非振荡细胞中降低[Ca2+]i的作用是通过激活KATP通道介导的。尽管有这种共同机制，但NE对振荡细胞和非振荡细胞有不同的影响。
