Calcium entry in rabbit corneal epithelial cells: evidence for a nonvoltage dependent pathway.
Calcium entry in rabbit corneal epithelial cells: evidence for a nonvoltage dependent pathway.
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兔角膜上皮细胞中的钙进入：非电压依赖性途径的证据。
DOI：
10.1007/bf00232803
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发表时间：
1995
期刊：
影响因子：
--
通讯作者：
Rae,JL
中科院分区：
文献类型：
--
作者：
Rich,A;Rae,JL
我们通过实验来阐明新鲜分散的兔角膜上皮细胞钙内流的途径。考虑了三种可能的途径：电压门控钙离子通道、Na+/Ca++交换和非电压依赖性钙离子渗透通道。电压钳技术未检测到携带Ca++或Ba++的全细胞内向电流。我们还使用成像技术和Ca++敏感比例染料fura 2来测量细胞内Ca++浓度的变化（[Ca]i）。含钙通道激动剂Bay-K-8644 （1 μm）的NaCl林格氏溶液或多种电压依赖性钙通道阻滞剂ni++ (40 μm)的NaCl林格氏溶液对[Ca++]i没有影响。用KCl林格液膜去极化导致[ca++]i下降。这些结果与电压门控ca++通道的存在不一致。另一方面，非电压门控的钙离子进入会因膜去极化而减少，并因膜超极化而增强。通过K+电流刺激而产生超极化的药剂，如氟芬那酸，导致比值强度增加。发现细胞对Mn++具有渗透性，而5 mmNi++减少的[Ca++]表明Ca++的传导被阻断。这些结果与非电压门控的Ca++内流途径最为一致。最后，用Li+代替细胞外的Na+会导致[Ca++]的增加，如果细胞首先使用Na+离子载体莫能菌素和瓦巴因（一种Na+-K+- atp酶抑制剂）装载Na+。这些结果表明Na+/Ca++交换也可能调节这种细胞类型中的[Ca++]。
We performed experiments to elucidate the calcium influx pathways in freshly dispersed rabbit corneal epithelial cells. Three possible pathways were considered: voltage-gated Ca++channels, Na+/Ca++exchange, and nonvoltage-dependent Ca++-permeable channels. Whole cell inward currents carrying either Ca++or Ba++were not detected using voltage clamp techniques. We also used imaging technology and the Ca++-sensitive ratiometric dye fura 2 to measure changes in intracellular Ca++concentration ([Ca]i). Bath perfusion with NaCl Ringer's solution containing the calcium channel agonist Bay-K-8644 (1 μm), or Ni++(40 μm), a blocker of many voltage-dependent calcium channels, did not affect [Ca++]i. Membrane depolarization with a KCl Ringer's bath solution resulted in adecreasein [Ca++]i. These results are inconsistent with the presence of voltage gated Ca++channels. Nonvoltage gated Ca++entry, on the other hand, would be reduced by membrane depolarization and enhanced by membrane hyperpolarization. Agents which hyperpolarize via stimulation of K+current, such as flufenamic acid, resulted in an increase in ratio intensity. The cells were found to be permeable to Mn++and bath perfusion with 5 mmNi++decreased [Ca++]isuggesting that the Ca++conductance was blocked. These results are most consistent with a nonvoltage gated Ca++influx pathway. Finally, replacing extracellular Na+with Li+resulted in an increase in [Ca++]iif the cells were first Na+-loaded using the Na+ionophore monensin and ouabain, a Na+-K+-ATPase inhibitor. These results suggest that Na+/Ca++exchange may also regulate [Ca++] in this cell type.