Oide H, Thurman R G
Department of Pharmacology, University of North Carolina at Chapel Hill 27599.
Hepatology. 1994 Oct;20(4 Pt 1):1009-14. doi: 10.1002/hep.1840200433.
Ito cells (fat-storing cells) have been implicated in mechanisms of liver fibrosis, and transforming growth factor-beta 1 is a key factor that stimulates collagen production by Ito cells. Moreover, Ito cells are reported to possess contractile proteins and to contract with ligands. We recently reported the presence of L-type voltage-operated Ca2+ channels in Kupffer cells. In this study, we examined whether Ito cells contain Ca2+ channels and also evaluated the effect of transforming growth factor-beta 1 on Ca2+ channels. Cytosolic free calcium concentration was measured in individual cultured Ito cells with the fluorescent Ca2+ indicator dye fura-2. Partial replacement of extracellular Na+ with K+ caused an increase in cytosolic free calcium, presumably as a result of transmembrane Ca2+ influx. Basal cytosolic free calcium levels were around 40 to 50 nmol/L in both control and transforming growth factor-beta 1-treated cells. In transforming growth factor-beta 1-treated cells, cytosolic free calcium increased in response to K+ at values as low as 10 mmol/L, whereas untreated cells did not respond. Half-maximal increases in cytosolic free calcium in transforming growth factor-beta 1-treated cells were observed with 63 +/- 6 mmol/L K+. With 100 mmol/L K+, intracellular free calcium increased around fourfold above basal values in transforming growth factor-beta 1-treated cells but was only increased about twofold in untreated controls. We conclude that this increase in cytosolic free calcium occurs by way of voltage-operated calcium channels; it did not occur in the absence of extracellular calcium and cannot be explained by Na+/Ca2+ exchange mechanisms.(ABSTRACT TRUNCATED AT 250 WORDS)
肝星状细胞（贮脂细胞）与肝纤维化机制有关，转化生长因子-β1是刺激肝星状细胞产生胶原蛋白的关键因子。此外，据报道肝星状细胞含有收缩蛋白并能与配体发生收缩反应。我们最近报道了库普弗细胞中存在L型电压门控Ca2+通道。在本研究中，我们检测了肝星状细胞是否含有Ca2+通道，并评估了转化生长因子-β1对Ca2+通道的影响。用荧光Ca2+指示剂染料fura-2测量单个培养的肝星状细胞中的胞质游离钙浓度。用K+部分替代细胞外Na+会导致胞质游离钙增加，这可能是跨膜Ca2+内流的结果。在对照细胞和经转化生长因子-β1处理的细胞中，基础胞质游离钙水平均在40至50 nmol/L左右。在经转化生长因子-β1处理的细胞中，胞质游离钙在低至10 mmol/L的K+浓度下就会增加，而未处理的细胞则无反应。经转化生长因子-β1处理的细胞中，胞质游离钙增加到最大值一半时所需的K+浓度为63±6 mmol/L。在100 mmol/L K+浓度下，经转化生长因子-β1处理的细胞内游离钙比基础值增加了约四倍，而未处理的对照细胞仅增加了约两倍。我们得出结论，这种胞质游离钙的增加是通过电压门控钙通道实现的；在没有细胞外钙的情况下不会发生，也不能用Na+/Ca2+交换机制来解释。（摘要截断于250字）
