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首页> 外文期刊>The European Journal of Neuroscience >No evidence for calcium electrogenic exchanger in frog semicircular canal hair cells.
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No evidence for calcium electrogenic exchanger in frog semicircular canal hair cells.

机译：青蛙半规管毛细胞中没有钙电交换剂的证据。

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We investigated the possibility that, in hair cells mechanically isolated from frog semicircular canals, Ca2+ extrusion occurs via a Na+ : Ca2+ (cardiac type) or a Na+ : Ca2+,K+ (retinal type) exchanger. Cells concurrently imaged during whole-cell patch-clamp recordings using the Ca2+ sensitive fluorescent dye Oregon Green 488 BAPTA-1 (100 micro m) showed no voltage dependence of Ca2+ clearance dynamics following a Ca2+ load through voltage-gated Ca2+ channels. Reverse exchange was probed in hair cells dialyzed with a Ca2+- and K+-free solution, containing a Na+ concentration that saturates the exchanger, after zeroing the contribution to the whole-cell current from Ca2+ and K+ conductances. In these conditions, no reverse exchange current was detected upon switching from a Ca2+-free external solution to a solution containing concentrations of Ca2+ alone, or Ca2+ + K+ that saturated the exchanger. By contrast, the same experimental protocol elicited peak exchange currents exceeding 100 pA in gecko rod photoreceptors, used as positive controls. In both cell types, we also probed the forward mode of the exchanger by rapidly increasing the intracellular Ca2+ concentration using flash photolysis of two novel caged Ca2+ complexes, calcium 2,2'-{[1-(2-nitrophenyl)ethane-1,2-diyl]bis(oxy)}bis(acetate) and calcium 2,2'-{[1-(4,5-dimethoxy-2-nitrophenyl)ethane-1,2-diyl]bis(oxy)} bis(acetate), in the presence of internal K+ and external Na+. No currents were evoked by UV-triggered Ca2+ jumps in hair cells, whereas exchanger conformational currents up to 400 pA, followed by saturating forward exchange currents up to 40 pA, were recorded in rod photoreceptors subjected to the same experimental conditions. We conclude that no functional electrogenic exchanger is present in this hair cell population, which leaves the abundant plasma membrane Ca2+-ATPases as the primary contributors to Ca2+ extrusion.
机译：我们调查了在从青蛙半规管机械隔离的毛细胞中，通过Na +：Ca2 +（心脏型）或Na +：Ca2 +，K +（视网膜型）交换剂发生Ca2 +挤出的可能性。在使用Ca2 +敏感荧光染料Oregon Green 488 BAPTA-1（100微米）进行全细胞膜片钳记录期间同时成像的细胞，显示在通过电压门控Ca2 +通道加载Ca2 +后，Ca2 +清除动力学没有电压依赖性。在将Ca2 +和K +电导对全细胞电流的贡献归零后，在用不含Ca2 +和K +的溶液透析的毛细胞中进行反向交换，该溶液含有使交换器饱和的Na +浓度。在这些条件下，当从无Ca2 +的外部溶液切换到仅包含Ca2 +浓度或使交换器饱和的Ca2 + + K +浓度的溶液时，未检测到反向交换电流。相比之下，相同的实验方案在用作阳性对照的壁虎杆感光器中引起了超过100 pA的峰值交换电流。在这两种细胞类型中，我们还使用两种新型笼状Ca2 +复合物，即2,2'-{[1-（2-（2-硝基苯基）乙烷-1， 2-二基]双（氧基）}双（乙酸盐）和2,2'-{[1-（4,5-二甲氧基-2-硝基苯基）乙烷-1,2-二基]双（氧基）}双（在内部K +和外部Na +的存在下）。在相同的实验条件下，在杆状光感受器中未记录到紫外线触发的毛细胞中Ca2 +跃迁引起的电流，而高达400 pA的交换器构象电流，接着是高达40 pA的饱和正向交换电流。我们得出的结论是，在该毛细胞群体中不存在功能性的电交换剂，从而使丰富的质膜Ca2 + -ATPases成为Ca2 +挤出的主要贡献者。

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