Gray M A, Pollard C E, Harris A, Coleman L, Greenwell J R, Argent B E
Department of Physiological Sciences, University Medical School, Newcastle upon Tyne, United Kingdom.
Am J Physiol. 1990 Nov;259(5 Pt 1):C752-61. doi: 10.1152/ajpcell.1990.259.5.C752.
Rat and human pancreatic duct cells have small-conductance Cl- channels in their apical plasma membranes. These channels are regulated by secretin and adenosine 3',5'-cyclic monophosphate and may function in parallel with Cl(-)-HCO3- exchangers to allow HCO3- secretion from the duct cell. Using the patch-clamp technique, we have now determined the anion permeability sequence of the channel as NO3- greater than Br- approximately I- approximately Cl- much greater than HCO3- much greater than gluconate. From this we conclude 1) that anion permeation involves a weak interaction with charged sites inside the channel pore, 2) that because of the low HCO3-/Cl- permeability ratio it is unlikely that significant amounts of HCO3- could be secreted directly via the channel, and 3) that channel permeability may determine the anion selectivity of secretion. We also show that 5-nitro-2-(3-phenylpropylamino)benzoic acid blocks the small-conductance Cl- channel, whereas 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid has no effect.
大鼠和人类胰腺导管细胞的顶端质膜中存在小电导氯离子通道。这些通道受促胰液素和3',5'-环磷酸腺苷调节，可能与Cl(-)-HCO3-交换体协同作用，使导管细胞分泌HCO3-。利用膜片钳技术，我们现已确定该通道的阴离子通透顺序为NO3-＞Br-≈I-≈Cl-＞＞HCO3-＞＞葡萄糖酸盐。据此我们得出以下结论：1）阴离子通透涉及与通道孔内带电荷位点的弱相互作用；2）由于HCO3-/Cl-通透率较低，大量HCO3-不太可能直接通过该通道分泌；3）通道通透性可能决定分泌的阴离子选择性。我们还表明，5-硝基-2-(3-苯丙基氨基)苯甲酸可阻断小电导氯离子通道，而4,4'-二异硫氰基芪-2,2'-二磺酸则无作用。
