Lack of evidence for vesicle trafficking of fluorescent bile salts
in rat hepatocyte couplets.
El-Seaidy, Adel Z., Charles O. Mills, Elwyn Elias, James M. Crawford.
Department of Pathology, Brigham and Women's Hospital, Harvard
Digestive Diseases Center, and Harvard Medical School, Boston, MA
02115 and Division of Gastroenterology, Queen's Hospital and
University of Birmingham, Birmingham B15 2TT, United Kingdom
APStracts 3:0160G, 1996.
The role of intracellular vesicles in the movement of bile salts
through hepatocytes from blood to bile has not been resolved. To
determine whether bile salts are sequestered during transit, rat
hepatocyte couplets were incubated with the fluorescent bile salts
cholyl-lysyl-fluorescein (CLF) and chenodeoxycholyl-lysyl-fluorescein
(CDCLF). Cellular and canalicular fluorescence were measured by
confocal scanning fluorescence micro scopy; inhomogeneity in
intracellular fluorescence was used to evaluate potential
sequestering of bile salts. Mean cellular and canalicular
fluorescence increased in parallel over 10 min, slightly exceeding
(p<0.05) the fold-increases in intracellular inhomogeneity. The
microtubule inhibitor, colchicine, had no effect on cellular or
canalicular fluorescence patterns. In contrast, the non-fluorescent
bile salt taurocholate enhanced the recovery of microtubules from
cold-induced depolymerization, measured by confocal
immunofluorescence of [beta]-tubulin. Thus, no evidence was obtained
for intra cellular sequestering of bile salts or microtubule
-dependent trafficking prior to cana licular secretion; cellular
uptake and distribution occurred in parallel with canalicular
secretion. The previously documented dependence of bile salt
secretion on intact microtubule function therefore appears to be an
indirect rather than a direct consequence of microtubule-dependent
events. In particular, enhanced microtubule assembly may play a role
in bile salt-induced delivery of bile salt transporters to the
canalicular membrane.
Received 6 June 1996; accepted in final form 12 August 1996.
APS Manuscript Number G229-6.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 August 1996