Extracellular calcium-sensing receptor is expressed in rat hepatocytes -: Coupling to intracellular calcium mobilization and stimulation of bile flow
Extracellular calcium-sensing receptor is expressed in rat hepatocytes -: Coupling to intracellular calcium mobilization and stimulation of bile flow
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DOI：
10.1074/jbc.m009317200
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发表时间：
2001-02-09
影响因子：
4.8
通讯作者：
Hendy, GN
中科院分区：
文献类型：
--
作者：
Canaff, L;Petit, JL;Hendy, GN
肝细胞对Ca-o（2+）的变化作出反应。受影响的肝功能包括胆汁分泌、代谢活性、肝脏再生和对外源性药物的反应。在目前的研究中，我们证明了细胞外钙感应受体（CASR）的存在，在肝脏中，在甲状旁腺和甲状腺以及肾脏中描述过。CASR mRNA在肝细胞中特异性表达，而在非实质肝细胞（星状细胞、内皮细胞和库普弗细胞）中不存在。使用特异性CASR抗体的Western blot分析显示，全肝和肝细胞提取物均有染色。大鼠肝脏切片的免疫组织化学和原位杂交显示，一部分肝细胞表达CASR蛋白和mRNA。已知的CASR激动剂钆（Gd3+; 0.5-3.0 mM）和精胺（1.25-20 mM），在缺乏Ca-o（2+）的情况下，在负载Fura-2/乙酰氧基甲酯的离体大鼠肝细胞中引起Ca-i（2+）的剂量相关增加。对任何一种激动剂的第二次挑战，反应都大大减弱。当肌醇1,4,5-三磷酸（IP3）敏感的钙池被thapsigargin或phenylephrine(一种α（1)-肾上腺素受体激动剂，已知可从IP3敏感的钙池中调动Ca-i(2+)）预处理后，这种反应也被取消。添加去氯苯基烷基胺化合物NPS R-467，而不添加S对映体NPS S-467，增加了Ca-i（2+）动员响应对1.25 mar精胺的敏感性。在Ca-o（2+）戒断后，胆汁停止流动，精胺在离体灌注肝制剂中增强其恢复。CASR激动剂Ca2+和Gd3+增加了胆汁流量，NPS R-467增强了对亚最大Ca2+浓度的反应，而S化合物则没有。因此，这些数据表明，大鼠肝细胞含有一种能够从ip3敏感储存中动员Ca-i（2+）的CASR，并且CASR的激活会刺激胆汁流动。
Liver cells respond to changes in Ca-o(2+). The hepatic functions affected include bile secretion, metabolic activity, liver regeneration, and the response to xenobiotics. In the present study, we demonstrate the presence, in the liver, of the extracellular calcium-sensing receptor (CASR), described previously in the parathyroid and thyroid glands and kidney. CASR mRNA was specifically expressed in hepatocytes and was absent in nonparenchymal liver cells (stellate, endothelial, and Kupffer cells). Western blot analysis using a specific CASR antibody showed staining in both whole liver and hepatocyte extracts. Immunohistochemistry and in situ hybridization of rat liver sections showed expression of CASR protein and mRNA by a subset of hepatocytes. The known agonists of the CASR, gadolinium (Gd3+; 0.5-3.0 mM) and spermine (1.25-20 mM), in the absence of Ca-o(2+), elicited dose-related increases in Ca-i(2+) in isolated rat hepatocytes loaded with Fura-2/acetoxymethyl ester. There was a greatly attenuated response to a second challenge with either agonist. The response was also abrogated when inositol 1,4,5-trisphosphate (IP3)-sensitive calcium pools had been depleted by pretreatment with either thapsigargin or phenylephrine, an alpha (1)-adrenergic receptor agonist known to mobilize Ca-i(2+) from IP,-sensitive pools. Addition of the deschloro-phenylalkylamine compound, NPS R-467, but not the S enantiomer, NPS S-467, increased the sensitivity of the Ca-i(2+) mobilization response to 1.25 mar spermine. Bile flow ceased after Ca-o(2+), withdrawal, and its recovery was enhanced by spermine in isolated perfused liver preparations. The CASR agonists Ca2+ and Gd3+ increased bile flow, and the response to a submaximal Ca2+ concentration was enhanced by NPS R-467 but not the S compound. Thus, the data indicate that rat hepatocytes harbor a CASR capable of mobilizing Ca-i(2+) from IP3-sensitive stores and that activation of the CASR stimulates bile flow.