Kuriu T, Nakaoka Y, Oosawa Y
International Institute for Advanced Research, Matsushita Electric Industrial Co. Ltd., Kyoto, Japan.
J Membr Biol. 1996 Nov;154(2):163-7. doi: 10.1007/s002329900141.
The concentration of intracellular calcium, [Ca2+]i, in Paramecium was imaged during cold-sensitive response by monitoring fluorescence of two calcium-sensitive dyes, Fluo-3 and Fura-Red. Cooling of a deciliated Paramecium caused a transient increase in [Ca2+]i at the anterior region of the cell. Increase in [Ca2+]i was not observed at any region in Ca(2+)-free solution. Under the electrophysiological recording, a transient depolarization of the cell was observed in response to cooling. On the voltage-clamped cell, cooling induced a transient inward current under conditions where K+ currents were suppressed. These membrane depolarizations and inward currents in response to cooling were lost upon removing extracellular Ca2+. The cold-induced inward current was lost upon replacing extracellular Ca2+ with equimolar concentration of Co2+, Mg2+ or Mn2+, but it was not affected significantly by replacing with equimolar concentration of Ba2+ or Sr2+. These results indicate that Paramecium cells have Ca2+ channels that are permeable to Ca2+, Ba2+ and Sr2+ in the anterior soma membrane and the channels are opened by cooling.
通过监测两种钙敏染料Fluo-3和Fura-Red的荧光，在草履虫冷敏反应期间对其细胞内钙浓度[Ca2+]i进行成像。去纤毛的草履虫冷却会导致细胞前部区域的[Ca2+]i瞬时增加。在无Ca(2+)溶液中的任何区域均未观察到[Ca2+]i增加。在电生理记录下，观察到细胞对冷却有瞬时去极化反应。在电压钳制的细胞上，在K+电流被抑制的条件下，冷却诱导出瞬时内向电流。去除细胞外Ca2+后，这些对冷却的膜去极化和内向电流消失。用等摩尔浓度的Co2+、Mg2+或Mn2+替代细胞外Ca2+后，冷诱导的内向电流消失，但用等摩尔浓度的Ba2+或Sr2+替代则对其无显著影响。这些结果表明，草履虫细胞在前体细胞体膜中有对Ca2+、Ba2+和Sr2+通透的Ca2+通道，且这些通道通过冷却打开。
