Journal of Lipid Research, Vol 36, 1729-1744, Copyright © 1995 by Lipid Research, Inc.
Synthesis and applicability of a photolabile 7,7-azi analogue of 3- sulfated taurine-conjugated bile salts
A Dietrich, W Dieminger, S MacNelly, W Gerok and G Kurz
Institut fur Organische Chemie und Biochemie, Universitat Freiburg, Germany.
For the identification of proteins involved in hepatobiliary transport, the
photolabile derivative 7,7-ASLCT ((7,7-azi-3 alpha-sulfato-5 beta-
cholan-24-oyl)-2'-aminoethanesulfonate) was synthesized. 7,7-ASLCT is taken
up into liver and excreted into bile completely unmetabolized at a rate
between the excretion rate of SLCT ((3 alpha-sulfato-5 beta-
cholan-24-oyl)-2'- aminoethanesulfonate) and SCCT ((7 alpha-hydroxy-3
alpha-sulfato-5 beta- cholan-24-oyl)-2'-aminoethanesulfonate). The
dependency of flux rate of uptake into freshly isolated hepatocytes on the
concentration of 7,7-ASLCT in presence of Na+ (143 mM) and with Na+
depletion (1 mM) is best described by the assumption of two simple
transport systems, the kinetic parameters of which are similar to those of
SLCT. As studied in the presence of Na+, 7,7-ASLCT and SLCT exhibit a
clearly competitive cross-inhibition of uptake with inhibition constants
that are similar to the corresponding half-saturation constants.
Photoaffinity labeling of isolated hepatocytes using 7,7- ASLCT (400
microM) resulted in the irreversible inhibition of the uptake of 7,7-ASLCT
and SLCT to similar extents, confirming the kinetic data that 7,7-ASLCT is
a true competing substrate for the uptake of SLCT. Because in intact rat
liver 7,7-ASLCT and SLCT mutually inhibit their biliary excretion, the
photolabile derivative shares with SLCT the same pathways in uptake and in
excretion. Thus, 7,7-ASLCT should be appropriate for the study of
hepatobiliary transport of sulfated and taurine-conjugated bile salts by
photoaffinity labeling.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
