Subcellular Regulation of Calcium Channel Currents in Renal Tubules.

我使用膜片钳技术鉴定和研究了培养的肾远端小管细胞（A6细胞）中的钙渗透通道。移液管溶液中含有（mM） Nagluconate 100, NaCl 20, MgCl_2 1, NaHEPES (pH 7.4) 10, EGTA 0.1-5。浴缸中要么含有正常的两栖动物溶液，要么含有不含Ca的溶液。在全细胞钳形记录中，ATP （0.2 ~ 20 uM）以平衡电位Cl （E_< Cl >=-47 mV）作用于细胞，诱导向内阳离子电流。当移液管中含有5毫米EGTA并将细胞置于无Ca溶液中时，电流几乎完全消失。用百日毒（1 ug/ml）预处理细胞，在细胞外Ca不存在的情况下，细胞内电流的激活速度减慢。当NaCl被CaCl_2（45）或CaCl_2 (22.5) + MnCl_2 (22.5)（mM）完全取代时，ATP在E_<cl> (-37 mV)下激活Ca和/或Mn电流。结论：外源ATP打开钙、锰渗透阳离子通道，该通道对细胞内钙活性敏感。

I have used the patch-clamp technique to identify and study Ca permeable channels in cultured renal distal tubule cells (A6 cells). The pipette solutions contained (in mM) Nagluconate 100, NaCl 20, MgCl_2 1, NaHEPES (pH 7.4) 10, EGTA 0.1-5. The bath either contained a normal amphibian solution or a Ca free solution. In the whole-cell clamp recording, the inward cation currents were induced by application of ATP (0.2-20 uM) to the cell at the equilibrium potential of Cl (E_<cl>=-47 mV). The currents were almost completely abolished when the pipette contained 5 mM EGTA and the cells were placed in a Ca free solution. Pretreatment of the cells with pertussis toxin (1 ug/ml)slowed the activation of the inward currents in the absence but not in the presence of extracellular Ca. When NaCl was totally replaced by CaCl_2 (45) or CaCl_2 (22.5) + MnCl_2 (22.5)(in mM), the Ca and/or Mn currents were evoked by ATP at E_<cl> (-37 mV). Conclusion: The external ATP opens the Ca and Mn permeable cation channel which is sensitive to the intracellular Ca activity.