O'Grady S M, Wolters P J
Department of Veterinary Biology, University of Minnesota, St. Paul 55108.
Am J Physiol. 1989 Jul;257(1 Pt 1):C45-51. doi: 10.1152/ajpcell.1989.257.1.C45.
Porcine gallbladder, stripped of serosal muscle, mounted in Ussing chambers, and bathed in plasma-like Ringer solution generates a serosal positive transepithelial potential of 4-7 mV and a short-circuit current (Isc) of 50-120 microA/cm2. Substitution of Cl with gluconate or HCO3 with N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) results in a 50% decrease in Isc. Treatment with 1 mM amiloride (mucosal side) or 0.1 mM acetazolamide (both sides) causes 25-27% inhibition of the Isc. Mucosal addition of 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid inhibits the Isc by 17%. Serosal addition of 0.1 mM bumetanide inhibits the Isc by 28%. Amiloride (1 mM) inhibits the net transepithelial fluxes of Na and Cl by 55 and 41%, respectively. Substitution of Cl with gluconate inhibits the net Na flux by 50%, whereas substitution of HCO3 with HEPES inhibits 85-90% of the net Na flux and changes Cl absorption to net secretion. Based on these results, it is hypothesized that Na and Cl transport across the apical membrane is mediated by two pathways, Na-H/Cl-HCO3 exchange and Na-HCO3 cotransport. Partial recycling of Cl and HCO3 presumably occurs through a Cl conductive pathway and Cl-HCO3 exchange, respectively, in the apical membrane. This results in net Na absorption, which accounts for most of the Isc observed under basal conditions. The effect of bumetanide on the basolateral membrane and the fact that Cl secretion occurs when HCO3 is absent suggests that Cl secretion involves a basolateral NaCl or Na-K-Cl cotransport system arranged in series with a Cl conductive pathway in the apical membrane.
去除浆膜肌层的猪胆囊，安装在尤斯灌流小室中，并置于类似血浆的林格氏溶液中，会产生4 - 7 mV的浆膜侧正跨上皮电位和50 - 120微安/平方厘米的短路电流（Isc）。用葡萄糖酸盐替代氯离子或用N - 2 - 羟乙基哌嗪 - N' - 2 - 乙烷磺酸（HEPES）替代碳酸氢根会使Isc降低50%。用1 mM氨氯吡咪（黏膜侧）或0.1 mM乙酰唑胺（两侧）处理会导致Isc受到25 - 27%的抑制。在黏膜侧添加4,4' - 二异硫氰基芪 - 2,2' - 二磺酸会使Isc受到17%的抑制。在浆膜侧添加0.1 mM布美他尼会使Isc受到28%的抑制。1 mM氨氯吡咪分别抑制钠和氯的净跨上皮通量55%和41%。用葡萄糖酸盐替代氯离子会使钠的净通量抑制50%，而用HEPES替代碳酸氢根会抑制85 - 90%的钠净通量，并使氯的吸收转变为净分泌。基于这些结果，推测钠和氯通过顶端膜的两种途径进行转运，即钠 - 氢/氯 - 碳酸氢根交换和钠 - 碳酸氢根共转运。氯离子和碳酸氢根可能分别通过顶端膜中的氯离子传导途径和氯 - 碳酸氢根交换进行部分再循环。这导致钠的净吸收，这是基础条件下观察到的大部分Isc的原因。布美他尼对基底外侧膜的作用以及在没有碳酸氢根时会发生氯分泌这一事实表明，氯分泌涉及一个基底外侧的氯化钠或钠 - 钾 - 氯共转运系统，该系统与顶端膜中的氯离子传导途径串联排列。
