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Intracellular transduction mechanism on the extracellular Ca^<2+>-sensing in parathyroid cells

甲状旁腺细胞胞外Ca^2感应的胞内转导机制

基本信息

批准号：
14540630
负责人：
OKADA Yukio
金额：
$ 2.24万
依托单位：
Nagasaki University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

Extracellular Ca^<2+> regulates the secretion of PTH from mammalian parathyroid cells through extracellular Ca^<2+>-sensing receptor(CaR). The transduction mechanism on the Ca^<2+>-sensing was investigated using the electrophysiological technique. Parathyroid cells were isolated from the parathyroid glands of bullfrogs. Under whole-cell mode with standard K^+ internal solution, frog parathyroid cells displayed resting potential of -30±2 mV (N=44). The mean input resistance and membrane capacitance were 13.7±0.9 GΩ and 7.6±0.2 pF, respectively. After attaining the whole-cell configuration in normal saline solution, almost all frog parathyroid cells displayed transient inward currents in response to depolarizing voltage steps from a holding potential of -84 mV. The inward currents disappeared by the replacement of external Na^+ with NMDG^+ and were reversibly inhibited by TTX, indicating that the currents occur through the TTX-sensitive voltage-gated Na^+ channels. When external Ca^<2+> level was increased from 1.8 to 10 mM, the parathyroid cells displayed a large increase in conductance. The reversal potential of the response shifted according to internal Cl^- concentration. The dialysis of 0.8 mM Ca^<2+> into the cells also induced niflumic acid-sensitive conductance. The extracellular Ca^<2+>-induced currents were strongly inhibited by external Gd^<3+> and intracellular U-73122. Intracellular dialysis of IP_3 did not elicit any response in the parathyroid cells, but the dialysis of ETYA induced large inward currents. The results suggest that extracellular Ca^<2+> rise elicits Ca^<2+>-activated Cl^- conductance in frog parathyroid cells through the arachidonic acid cascade.

细胞外钙离子通过胞外钙敏感受体(CAR)调节哺乳动物甲状旁腺细胞甲状旁腺激素的分泌。用电生理技术研究了钙离子敏感的信号转导机制。从牛蛙甲状旁腺中分离出甲状旁腺细胞。在标准K+内液的全细胞模式下，蛙甲状旁腺细胞的静息电位为-30±2 mV(N=44)。平均输入电阻为13.7±0.9GΩ，膜电容为7.6±0.2pF。在生理盐水溶液中达到全细胞构型后，几乎所有的蛙甲状旁腺细胞都表现出瞬时内向电流，这是对保持电位为-84 mV的去极化电压阶跃的响应。用NMDG^+替代外源性Na~(++)后，内向电流消失，并被TTX可逆地抑制，表明电流是通过TTX敏感的电压门控性Na~(++)通道发生的。当外界钙离子浓度从1.8 mM增加到10 mM时，甲状旁腺细胞的电导有较大幅度的增加。该反应的反转电位随内部氯离子浓度的变化而变化。细胞内透析0.8 mM Ca~(2+)和Gt~(2+)也可引起尼氟米酸敏感的电导。外源性Gd^&lt；3+&gt；和胞内U-73122对胞外Ca~(2+)~(2+)诱发电流有强烈的抑制作用。细胞内透析IP_3不引起甲状旁腺细胞的反应，而透析ETYA则引起较大的内向电流。结果提示，细胞外Ca~(2+)升高通过花生四烯酸级联途径引起甲状旁腺细胞内Ca~(2+)~(2+)&Gt~(2+)电导升高。