Marvão P, De Jesus Ferreira M C, Bailly C, Paulais M, Bens M, Guinamard R, Moreau R, Vandewalle A, Teulon J
INSERM CJF 95-07, Institut Fédératif de Recherche 02, Faculté de Médecine Xavier Bichat, Paris, France.
J Clin Invest. 1998 Dec 1;102(11):1986-93. doi: 10.1172/JCI4074.
The cortical thick ascending limb (CTAL) absorbs Cl- via a Na+-K+-Cl- cotransport at the apical membrane and several Cl- channels at the basolateral membrane, including a 9-pS channel having several properties of the cystic fibrosis transmembrane conductance regulator (CFTR). Having checked that CFTR mRNA is present in the mouse CTAL, we investigated whether this channel is a CFTR molecule by applying the patch-clamp technique to CTALs microdissected from CFTR knockout mice (cftrm1Unc). The 9-pS channel was active in cell-attached patches from tubules of mice homozygous for the disrupted cftr gene [CFTR (-/-)] at the same frequency and with the same activity (NPo) as in normal [CFTR (+/+)] or heterozygous [CFTR (+/-)] mice. The conductive properties of the channel, studied on inside-out patches, were identical in CFTR (-/-), CFTR (+/+), and CFTR (+/-) tubules, as were the sensitivities to internal pH and internal ATP, two typical features of this channel. In addition, the Cl- absorption in isolated, microperfused CTALs and the Na+-K+-Cl- cotransport activity were identical in CFTR (-/-), CFTR (+/+), and CFTR (+/-) mice. These results show that the 9-pS Cl- channel is distinct from CFTR, and that the CFTR protein has no influence on the Cl- absorption in this part of the renal tubule.
皮质厚升支（CTAL）通过顶端膜上的钠钾氯共转运体和基底外侧膜上的几种氯通道吸收氯离子，其中包括一种具有囊性纤维化跨膜传导调节因子（CFTR）多种特性的9皮西门子通道。在确认小鼠CTAL中存在CFTR mRNA后，我们通过对从CFTR基因敲除小鼠（cftrm1Unc）显微解剖得到的CTAL应用膜片钳技术，研究该通道是否为CFTR分子。在cftr基因缺失的纯合小鼠[CFTR（-/-）]肾小管的细胞贴附膜片中，9皮西门子通道的活性与正常[CFTR（+/ +）]或杂合[CFTR（+/-）]小鼠的活性频率相同且活性（NPo）相同。在反转膜片上研究的该通道的导电特性在CFTR（-/-）、CFTR（+/ +）和CFTR（+/-）肾小管中是相同的，对内部pH和内部ATP的敏感性也是如此，这是该通道的两个典型特征。此外，在CFTR（-/-）、CFTR（+/ +）和CFTR（+/-）小鼠中，分离的显微灌注CTAL中的氯吸收和钠钾氯共转运活性是相同的。这些结果表明，9皮西门子氯通道与CFTR不同，并且CFTR蛋白对肾小管这一部分的氯吸收没有影响。
