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Importance of Solvent Drag and Diffusion in Bile Acid‐Dependent Bile Formation: Ion Substitution Studies in Isolated Perfused Rat Liver
Author(s) -
Sawkat ANWER M.,
Hegner Dietmar
Publication year - 2007
Publication title -
hepatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.488
H-Index - 361
eISSN - 1527-3350
pISSN - 0270-9139
DOI - 10.1002/hep.1840020511
Subject(s) - chemistry , choline , solvent drag , bile acid , solvent , diffusion , osmotic concentration , inorganic chemistry , medicine , biochemistry , crystallography , microstructure , physics , grain boundary , thermodynamics
Ion substitution studies were carried out in the isolated perfused rat liver to define the importance of solvent drag and diffusion in bile acid‐dependent bile formation. Two different methods, namely single injection (20 μmoles) and continuous infusions at 0.4, 0.8, 1.2, and 1.6 μmoles per min taurocholate (TC), were used to determine the bile acid‐dependent bile flow (BADF). Both methods gave essentially the same results. Replacement of Na + (146 m M ) by 120 or 146 m M Li + and Cl − (127 m M ) by 120 m M NO 3 − increased BADF significantly. On the other hand, replacement of Na + by 120 m M choline and Cl − by 120 m M isethionate decreased the BADF. The osmolarity of TC solution was not different when Na + was replaced by 120 m M Li + or choline and TC did not affect the osmotic activity of NaCl, LiCl, and choline‐Cl differently. Thus, the observed effect of Na + replacement on BADF is not due to any change in the osmotic activity of the secreted TC. Substitution of HCO 3 − by equimolar tricine also decreased BADF. Under this condition, BADF increased when NaCl was replaced by equimolar NaN0 3 . Thus, HCO 3 ” does not seem to be essential for TC choleresis. Since Li + and NO 3 ” are more permeable, and choline and isethionate are less permeable than Na + and Cl − , respectively, these results suggest that the BADF is dependent on the permeability of the substituting cations and anions and thus support the hypothesis that solvent drag and diffusion play an important role in BADF.