RT Journal Article
SR Electronic
T1 Canalicular Membrane Transport Is Primarily Responsible for the Difference in Hepatobiliary Excretion of Triethylmethylammonium and Tributylmethylammonium in Rats
JF Drug Metabolism and Disposition
JO Drug Metab Dispos
FD American Society for Pharmacology and Experimental Therapeutics
SP 872
OP 879
VO 27
IS 8
A1 Han, Yong-Hae
A1 Chung, Suk-Jae
A1 Shim, Chang-Koo
YR 1999
UL http://dmd.aspetjournals.org/content/27/8/872.abstract
AB Two structurally similar quaternary ammonium compounds, triethylmethylammonium (TEMA, Mr 116) and tributylmethylammonium (TBuMA, Mr 200) were used as model compounds to identify the unit process of hepatobiliary excretion that is responsible for markedly different biliary excretion of organic cations (OCs). Cumulative biliary excretion (in percentage of dose; i.v., 12 μmol/kg) was 0.17 for TEMA and 34.5 for TBuMA. In vivo uptake clearance into the liver was 0.686 ± 0.020 ml/min for TEMA and 0.421 ± 0.028 ml/min for TBuMA. When the uptake clearance was examined in an isolated hepatocyte system, comparable clearance between TEMA and TBuMA was obtained, consistent with the in vivo result. These observations suggest that uptake into the liver is not the major determinant for the difference in biliary excretion of the OCs. Coadministration of colchicine, an inhibitor of microtubule formation, had no effect on biliary excretion of the model compounds, and the primary site of subcellular distribution of the OCs appears to be the cytosol, suggesting that intracellular movement does not play a major role in the markedly different biliary excretion of the OCs. In contrast, in vivo excretion clearance across the canalicular membrane for TBuMA was 180-fold greater than that for TEMA, and in vitro efflux clearance of TBuMA was smaller than that of TEMA (p < .01), indicative of involvement of these processes in the markedly different biliary excretion of the OCs. Therefore, these data indicate that canalicular transport is primarily responsible for the markedly different biliary excretion of TEMA and TBuMA. The American Society for Pharmacology and Experimental Therapeutics