Villanger O, Veel T, Raeder M G
Institute for Experimental Medical Research, Ullevaal Hospital, University of Oslo, Norway.
Am J Physiol. 1993 Oct;265(4 Pt 1):G719-24. doi: 10.1152/ajpgi.1993.265.4.G719.
Intrahepatic bile duct epithelial cells contribute to bile formation by hormone-dependently secreting HCO3- to bile and H+ to periductular fluid. The present study was undertaken to determine whether the secretin-induced H+ secretion is due to activation of a H(+)-ATPase or Na(+)-H+ exchange. H+ secretion was estimated from the rate of intracellular pH (pHi) recovery after acid loading (24 mM NH4Cl) of microdissected bile ductules from pig liver mounted in a flow-through chamber on the stage of a microscope. pHi was measured from an estimated average of 10-15 epithelial cells using the fluorescent pHi indicator 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein and dual-wavelength excitation of fluorescence. The ducts were superfused with HCO3(-)-free N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid buffers. We found that secretin induced net H+ secretion of 4.53 +/- 0.7 mumol.ml cell volume-1 x min-1. This H+ secretion was blocked by 10(-6) M bafilomycin A1 but was unaffected by Na+ substitution with choline in the superfusion buffer. The experiments also showed that bafilomycin A1 did not block Na(+)-H+ exchange. The secretin-induced H+ secretion is probably caused by a vacuolar-type H(+)-ATPase and may constitute an important element of the cellular mechanisms causing secretin-dependent ductular HCO3- secretion into bile.
肝内胆管上皮细胞通过激素依赖性地向胆汁中分泌HCO3-并向胆管周围液中分泌H+来促进胆汁形成。本研究旨在确定促胰液素诱导的H+分泌是由于H(+)-ATP酶的激活还是Na(+)-H+交换。通过安装在显微镜载物台上的流通室中来自猪肝的显微解剖胆管小管在酸负荷（24 mM NH4Cl）后细胞内pH（pHi）恢复率来估计H+分泌。使用荧光pHi指示剂2',7'-双（羧乙基）-5,6-羧基荧光素和双波长荧光激发，从估计的10-15个上皮细胞的平均值测量pHi。用不含HCO3(-)的N-2-羟乙基哌嗪-N'-2-乙烷磺酸缓冲液对胆管进行灌流。我们发现促胰液素诱导的净H+分泌为4.53±0.7 μmol·ml细胞体积-1×min-1。这种H+分泌被10(-6) M巴弗洛霉素A1阻断，但在灌流缓冲液中用胆碱替代Na+时不受影响。实验还表明巴弗洛霉素A1不阻断Na(+)-H+交换。促胰液素诱导的H+分泌可能是由液泡型H(+)-ATP酶引起的，并且可能构成导致促胰液素依赖性胆管HCO3-分泌到胆汁中的细胞机制的重要组成部分。
