Activation of different Cl currents in Xenopus oocytes by Ca liberated from stores and by capacitative Ca influx

被引:82
作者
Hartzell, HC
机构
[1] Dept. of Anatomy and Cell Biology, Emory University, School of Medicine, Atlanta
关键词
Xenopus oocytes; inositol phosphate; Cl channels; calcium; Ca channels;
D O I
10.1085/jgp.108.3.157
中图分类号
Q4 [生理学];
学科分类号
071003 ;
摘要
Xenopus oocytes are an excellent model system for studying Ca signaling. The purpose of this study was to characterize in detail the Ca-activated Cl currents evoked by injection of inositol 1,4,5-trisphosphate (IP3) into Xenopus oocytes voltage-clamped with two microelectrodes. Injection of IP3 into Xenopus oocytes activates two different Ca-activated Cl currents. I-Cl-1 is stimulated rapidly (within 5 s after IP3 injection), exhibits time-dependent activation upon depolarization, a linear instantaneous ni relationship with a reversal potential near Eo, and a curvilinear activation curve with an approximate half-maximal activation Voltage of >200 mV. I-Cl-2D is stimulated slowly after IP3 injection (half-maximal stimulation occurs similar to 3 min after injection). I-Cl-2D has a strongly outwardly rectifying instantaneous IV relationship with a reversal potential near E(Cl) and is activated by hyperpolarization with a half-maximal activation voltage of -105 mV. I-Cl-2D cannot be activated by Ca released from stores but is activated by Ca influx. In contrast, I-Cl-1 can be stimulated by Ca released from intracellular Ca stores. It can also be stimulated by Ca influx through store-operated channels if the Ca driving force is increased by a hyperpolarization immediately before the depolarization that gates I-Cl-1 channels. The description of two currents activated by influx and Ca release from stores provides new insights into and questions about the regulation of Ca in Xenopus oocytes.
引用
收藏
页码:157 / 175
页数:19
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