Elsing C, Hirlinger A, Renner E L, Lauterburg B H, Meier P J, Reichen J
Department of Clinical Pharmacology, University of Berne, Switzerland.
Biochem J. 1995 Apr 1;307 ( Pt 1)(Pt 1):175-81. doi: 10.1042/bj3070175.
2H2O affects many membrane transport processes by solvent and kinetic isotope effects. Since bile formation is a process of osmotic filtration where such effects could be important, we investigated the effects of 2H2O on bile formation in the in situ perfused rat liver. Dose finding experiments showed that at high concentrations, 2H2O increased vascular resistance and induced cholestasis; at 60% 2H2O however, a clear dissociation between the vascular and biliary effects was observed. Therefore, further experiments were carried out at this concentration. The main finding was a reduction in bile salt-independent bile flow from 0.99 +/- 0.04 to 0.66 +/- 0.04 microliters.min-1.g-1 (P < 0.001). This was associated with a 40% reduction in biliary bicarbonate concentration (P < 0.001). Choleretic response to neither taurocholate nor ursodeoxycholate was altered by 2H2O; in particular, there was a similar stimulation of bicarbonate secretion by ursodeoxycholate in the presence of 60% 2H2O. To further elucidate this phenomenon, the effect of 2H2O on three proteins potentially involved in biliary bicarbonate secretion was studied in vitro. 2H2O slightly inhibited cytosolic carboanhydrase and leukocyte Na+/H(+)-exchange, these effects reached statistical significance at 100% 2H2O only, however. In contrast, Cl-/HCO(3-)-exchange in canalicular membrane vesicles was already inhibited by 50% (P < 0.001) at 60% 2H2O. Finally, there was a slight reduction in biliary glutathione secretion while that of the disulphide was not affected. Our results are compatible with an inhibition of canalicular Cl-/HCO(3-)-exchange by 2H2O. Whether this is due to altered hydration of the exchanger and/or of the transported bicarbonate remains to be determined.
2H₂O 通过溶剂和动力学同位素效应影响许多膜转运过程。由于胆汁形成是一个渗透过滤过程，在这个过程中这些效应可能很重要，我们研究了 2H₂O 对原位灌注大鼠肝脏胆汁形成的影响。剂量探索实验表明，高浓度时，2H₂O 增加血管阻力并诱导胆汁淤积；然而，在 60% 2H₂O 时，观察到血管和胆汁效应之间明显分离。因此，在此浓度下进行了进一步实验。主要发现是不依赖胆盐的胆汁流量从 0.99±0.04 降至 0.66±0.04 微升·分钟⁻¹·克⁻¹（P<0.001）。这与胆汁中碳酸氢盐浓度降低 40%相关（P<0.001）。2H₂O 对牛磺胆酸盐和熊去氧胆酸盐的利胆反应均无改变；特别是，在 60% 2H₂O 存在下，熊去氧胆酸盐对碳酸氢盐分泌有类似的刺激作用。为进一步阐明这一现象，在体外研究了 2H₂O 对三种可能参与胆汁碳酸氢盐分泌的蛋白质的影响。2H₂O 轻微抑制胞质碳酸酐酶和白细胞 Na⁺/H⁺交换，但这些效应仅在 100% 2H₂O 时达到统计学显著意义。相反，在 60% 2H₂O 时，胆小管膜囊泡中的 Cl⁻/HCO₃⁻交换已被抑制 50%（P<0.001）。最后，胆汁谷胱甘肽分泌略有减少，而二硫化物的分泌未受影响。我们的结果与 2H₂O 抑制胆小管 Cl⁻/HCO₃⁻交换一致。这是否是由于交换体和/或转运的碳酸氢盐的水合作用改变仍有待确定。
