Sakai H, Saito T
Institute of Biological Sciences, University of Tsukuba, Ibaraki, Japan.
J Neurobiol. 1997 Apr;32(4):377-90. doi: 10.1002/(sici)1097-4695(199704)32:4<377::aid-neu2>3.0.co;2-3.
We cultured retinal pigment epithelial (RPE) cells dissociated from adult newt eye and analyzed their voltage-gated ion channels during culture using whole-cell patch-clamp techniques. The results were compared with those of retinal neurons under identical experimental conditions. After 6-9 days in culture (early stage), > 60% of RPE cells developed voltage-gated Na+ and Ca2+ channels that were not observed in freshly dissociated RPE cells. The number of cells expressing Na+ channels and Na+ current density were high after 12-15 days in culture (intermediate stage), while the number of Ca2+ channel-expressing cells and Ca2+ current density were high after 20-30 days in culture (late stage). The activation voltage of the Na+ current in the RPE cells was similar to that in neurons. The voltage dependence of Na+ current inactivation was somewhat different between two cell types. The steepness of the inactivation curve tended to be less in cultured RPE cells than in neurons, and the half-inactivation voltage was about-54 mV for the RPE cells and -45 mV for neurons. The Ca2+ current expressed in cultured RPE cells was too small to detect without replacement of external Ca2+ with Ba2+. The Ba2+ current, like Ca2+ current in neurons, was enhanced by Bay-K 8644 and blocked by nicardipine. These results suggest that the RPE cells, like neurons, expressed L-type Ca2+ channels in culture. The possibility that the development of both Na2+ and Ca2+ channels in cultured RPE cells is a manifestation of the transdifferentiation of RPE cells into neurons is discussed.
我们培养了从成年蝾螈眼睛分离出的视网膜色素上皮（RPE）细胞，并使用全细胞膜片钳技术在培养过程中分析了它们的电压门控离子通道。将结果与相同实验条件下视网膜神经元的结果进行了比较。在培养6 - 9天（早期）后，超过60%的RPE细胞形成了在刚分离的RPE细胞中未观察到的电压门控Na⁺和Ca²⁺通道。培养12 - 15天（中期）后，表达Na⁺通道的细胞数量和Na⁺电流密度较高，而培养20 - 30天（后期）后，表达Ca²⁺通道的细胞数量和Ca²⁺电流密度较高。RPE细胞中Na⁺电流的激活电压与神经元中的相似。两种细胞类型之间Na⁺电流失活的电压依赖性有所不同。培养的RPE细胞中失活曲线的陡峭程度往往比神经元中的小，RPE细胞的半失活电压约为 - 54 mV，神经元的为 - 45 mV。培养的RPE细胞中表达的Ca²⁺电流太小，在不将外部Ca²⁺替换为Ba²⁺的情况下无法检测到。Ba²⁺电流与神经元中的Ca²⁺电流一样，被Bay - K 8644增强并被尼卡地平阻断。这些结果表明，RPE细胞在培养中与神经元一样表达L型Ca²⁺通道。讨论了培养的RPE细胞中Na⁺和Ca²⁺通道的发育是RPE细胞向神经元转分化的表现的可能性。
