Hirsch J R, Weber G, Kleta I, Schlatter E
Westfälische Wilhelms-Universität Münster, Medizinische Poliklinik, Experimentelle Nephrologie, Münster, Germany.
Cell Physiol Biochem. 2001;11(2):77-82. doi: 10.1159/000047794.
Recently we showed that a K(+) channel in immortalized human kidney epithelial (IHKE-1) cells derived from the proximal tubule is regulated by natriuretic peptides in cell-attached patches and directly regulated by cGMP in excised inside-out oriented membrane patches [1]. The patch clamp technique was used to investigate the regulatory effect of extracellular, non-membrane permeable cGMP on membrane voltage and the regulation of this K(+) channel in outside-out oriented membrane patches. In 7 out of 7 experiments the membrane voltage of IHKE-1 cells depolarized by 3.9 +/- 0.1 mV when the non-membrane permeable cGMP was added to the bath solution. In outside-out oriented membrane patches cGMP inhibited P(o) already at 1 microM (-12 +/- 4%, n=7), at 0.1 mM inhibition of P(o) reached -39 +/- 6% (n=14). cAMP (0.1 mM) only had a weak inhibitory effect (n=7). GTP and ATP (n=7 each) had no significant effect on P(o) from the outside. When cGMP was added to the pipette solution in experiments with outside-out oriented membranes cGMP still inhibited this K(+) channel from the outside by 36 +/- 6% (n=6). In 4 paired experiments 8-Br-cGMP (0.1 mM) showed a significantly higher inhibitory effect on P(o) compared to cGMP (0.1 mM). cGMP inhibits a K(+) channel in human proximal tubule cells from the outside and may serve as an autocrine and paracrine regulatory factor in the kidney.
最近我们发现，源自近端小管的永生化人肾上皮细胞（IHKE-1）中的一种钾离子通道，在细胞贴附式膜片钳中受利钠肽调节，在切除的内向外膜片中直接受环鸟苷酸（cGMP）调节[1]。采用膜片钳技术研究细胞外、非膜通透的cGMP对膜电压的调节作用，以及在向外膜片中对该钾离子通道的调节。在7个实验中的7个里，当向浴液中添加非膜通透的cGMP时，IHKE-1细胞的膜电压去极化3.9±0.1 mV。在向外膜片中，cGMP在1微摩尔时就已抑制开放概率（P(o)）（-12±4%，n = 7），在0.1毫摩尔时P(o)的抑制率达到-39±6%（n = 14）。环磷酸腺苷（cAMP，0.1毫摩尔）仅有微弱的抑制作用（n = 7）。鸟苷三磷酸（GTP）和三磷酸腺苷（ATP）（各n = 7）对膜外侧的P(o)无显著影响。在向外膜片实验中，当将cGMP添加到吸管溶液中时，cGMP仍能从膜外侧抑制该钾离子通道36±6%（n = 6）。在4个配对实验中，8-溴环鸟苷酸（8-Br-cGMP，0.1毫摩尔）对P(o)的抑制作用明显高于cGMP（0.1毫摩尔）。cGMP从细胞外抑制人近端小管细胞中的钾离子通道，可能作为肾脏中的自分泌和旁分泌调节因子。
