T. Kamisako et I. Leier, Characterization of ATP-dependent monoglucuronosyl bilirubin transport across rat canalicular membrane vesicles, HEPATOL RES, 19(2), 2001, pp. 103-107
Bilirubin conjugates are secreted from hepatocytes into bile. Monoglucurono
syl bilirubin is an endogenous substrate for the multidrug resistance prote
in ?, which is located in rat hepatocyte canalicular membrane. We have char
acterized this ATP-dependent transport using rat canalicular membrane vesic
les. Monoglucuronosyl bilirubin, H-3-labeled in the glucuronosyl moiety, wa
s synthesized enzymatically using recombinant UDP-glycosyltransferase 1Al,
and was stabilized with ascorbate. The rate for ATP-dependent transport of
monoglucuronosyl bilirubin (at 0.5 muM) was 7.3 +/- 1.1 pmol mg protein(-1)
min(-1) and the K-m value was 1.3 +/- 0.4 muM. This is the first time to d
emonstrate this kinetic constant of monoglucuronosyl bilirubin for the rat
hepatocyte canalicular membrane. The K-m value is similar to one for recomb
inant rat multidrug resistance protein 2. (C) 2001 Elsevier Science Ireland
Ltd. All rights reserved.