Volk T, Frömter E, Korbmacher C
Zentrum der Physiologie, Johann Wolfgang Goethe-Universität, Frankfurt am Main, Germany.
Proc Natl Acad Sci U S A. 1995 Aug 29;92(18):8478-82. doi: 10.1073/pnas.92.18.8478.
We investigated the effect of cell shrinkage on whole-cell currents of M-1 mouse cortical collecting duct cells. Addition of 100 mM sucrose to an isotonic NaCl bath solution induced cell shrinkage and increased whole-cell currents within 5-10 min by approximately 12-fold. The effect was reversible upon return to isotonic solution and could also be elicited by adding 100 mM urea or 50 mM NaCl. Replacement of bath Na+ by K+, Cs+, Li+, or Rb+ did not significantly affect the stimulated inward current, but replacement by N-methyl-D-glucamine reduced it by 88.1 +/- 1.3% (n = 34); this demonstrates that hypertonicity activates a nonselective alkali cation conductance. The activation was independent of extra- and intracellular Ca2+, but 1 or 10 mM ATP in the pipette suppressed it in a concentration-dependent manner, indicating that intracellular ATP levels may modulate the degree of channel activation. Flufenamic acid (0.1 mM) and gadolinium (0.1 mM) inhibited the stimulated current by 68.7 +/- 5.9% (n = 9) and 32.4 +/- 11.7% (n = 6), respectively, whereas 0.1 mM amiloride had no significant effect. During the early phase of hypertonic stimulation single-channel transitions could be detected in whole-cell current recordings, and a gradual activation of 30 and more individual channels with a single-channel conductance of 26.7 +/- 0.4 pS (n = 29) could be resolved. Thus, we identified the nonselective cation channel underlying the shrinkage-induced whole-cell conductance that may play a role in volume regulation.
我们研究了细胞皱缩对M-1小鼠皮质集合管细胞全细胞电流的影响。向等渗NaCl浴液中添加100 mM蔗糖可诱导细胞皱缩，并在5-10分钟内使全细胞电流增加约12倍。回到等渗溶液后，该效应是可逆的，添加100 mM尿素或50 mM NaCl也可引发此效应。用K+、Cs+、Li+或Rb+替代浴液中的Na+对刺激的内向电流没有显著影响，但用N-甲基-D-葡糖胺替代则使其降低了88.1±1.3%（n = 34）；这表明高渗激活了一种非选择性碱阳离子电导。该激活与细胞外和细胞内的Ca2+无关，但移液管中1或10 mM的ATP以浓度依赖的方式抑制了它，表明细胞内ATP水平可能调节通道激活的程度。氟芬那酸（0.1 mM）和钆（0.1 mM）分别使刺激电流抑制了68.7±5.9%（n = 9）和32.4±11.7%（n = 6），而0.1 mM的氨氯吡咪没有显著影响。在高渗刺激的早期阶段，可在全细胞电流记录中检测到单通道转换，并且可以分辨出逐渐激活30个及更多单个通道，其单通道电导为26.7±0.4 pS（n = 29）。因此，我们确定了收缩诱导的全细胞电导背后的非选择性阳离子通道，其可能在体积调节中起作用。
