URSODEOXYCHOLATE MOBILIZES INTRACELLULAR CA-2+ AND ACTIVATES PHOSPHORYLASE-A IN ISOLATED HEPATOCYTES
URSODEOXYCHOLATE MOBILIZES INTRACELLULAR CA-2+ AND ACTIVATES PHOSPHORYLASE-A IN ISOLATED HEPATOCYTES
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DOI：
10.1152/ajpgi.1993.264.2.g243
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发表时间：
1993-02-01
影响因子：
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通讯作者：
NUSSBAUM, R
中科院分区：
文献类型：
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作者：
BOUSCAREL, B;FROMM, H;NUSSBAUM, R
在离体仓鼠肝细胞中，熊去氧胆酸（UDCA）动员细胞内游离钙（[Ca 2 +]i）和激活磷酸化酶a，半最大有效浓度分别为188和9 μ M。加入乙二醇-双（β-氨基乙基醚）-N，N，N '，N'-四乙酸（EGTA）不影响UDCA动员的最大[Ca 2 +]i;然而，[Ca 2 +]i在4-5 min内恢复至基础水平，而不加EGTA时>10 min。UDCA和加压素在存在和不存在细胞外Ca 2+的情况下均以相同程度激活磷酸化酶a，当细胞内Ca 2+耗尽时，两种药物的作用均被消除。 当与500 μ M UDCA联合时，加压素（100 nM）不能进一步动员[Ca 2 +]i或激活磷酸化酶a。然而，与加压素不同，UDCA不刺激肌醇1，4，5-三磷酸（IP 3）形成。与牛磺酸结合的UDCA（TUDCA）相反，浓度小于或等于500 μ M的甘氨酸结合的UDCA（GUDCA）不影响[Ca 2 +]i或磷酸化酶a。石胆酸和牛磺石胆酸（TLCA）显示出最高的亲和力的Ca 2+。此外，TLCA，鹅去氧胆酸，和氟化钠刺激Ca 2+流出的浓度低至100 μ M，200 μ M，和5 mM，分别。相反，UDCA、TUDCA和GUDCA对Ca 2+的亲和力最低，对Ca 2+流出无影响。当TLCA与UDCA、TUDCA或GUDCA联合使用时，TLCA单独诱导的Ca 2+释放增加28%，进一步增加至约60%。然而，UDCA及其结合物并未进一步增加NaF诱导的Ca 2+外流。这些研究表明，UDCA通过IP 3非依赖性Ca 2+依赖性机制激活磷酸化酶a。此外，UDCA对Ca 2+的亲和力较低，不会刺激Ca 2+外流。
In isolated hamster hepatocytes, ursodeoxycholic acid (UDCA) mobilized intracellular free calcium ([Ca2+]i) and activated phosphorylase a with a half-maximally effective concentration of 188 and 9 muM, respectively. Addition of ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) did not affect the maximum [Ca2+]i mobilized by UDCA; however, [Ca2+]i returned to basal levels in 4-5 min compared with >10 min in the absence of EGTA. Both UDCA and vasopressin activated phosphorylase a to the same extent in the presence and absence of extracellular Ca2+, and the effect of both agents was abolished when the cells were depleted in Ca2+. Vasopressin (100 nM) did not further mobilize [Ca2+]i or activate phosphorylase a when combined with 500 muM UDCA. However, unlike vasopressin, UDCA did not stimulate inositol 1,4,5-trisphosphate (IP3) formation. In contrast to taurine-conjugated UDCA (TUDCA), concentrations less-than-or-equal-to 500 muM of glycine-conjugated UDCA (GUDCA) did not affect either [Ca2+]i or phosphorylase a. Lithocholic acid and taurolithocholic acid (TLCA) displayed the highest affinity for Ca2+. In addition, TLCA, chenodeoxycholic acid, and NaF stimulated Ca2+ efflux at concentrations as low as 100 muM, 200 muM, and 5 mM, respectively. Conversely, UDCA, TUDCA, and GUDCA presented the lowest affinity for Ca2+ and had no effect on Ca2+ efflux. The 28% increase in Ca2+ release induced by TLCA alone was further augmented to approximately 60% when TLCA was combined with UDCA, TUDCA, or GUDCA. However, Ca2+ efflux induced by NaF was not further increased by UDCA and its conjugates. These studies suggest that UDCA activates phosphorylase a through an IP3-independent Ca2+-dependent mechanism. Furthermore, UDCA presents a low affinity for Ca2+ and does not stimulate Ca2+ efflux.