Transport activity of human MRP3 expressed in Sf9 cells: comparative studies with rat MRP3.
OBJECTIVE
Multidrug resistance-associated protein 3 (MRP3) was initially cloned as a hepatic transporter induced under cholestatic/ hyperbilirubinemic conditions. In the present study, transport property of human MRP3 (hMRP3) was compared with that of rat MRP3 (rMRP3).


METHODS
Adenosine 5' triphosphate (ATP)-dependent uptake of several organic anions into the membrane vesicles isolated from the Sf9 cells expressing hMRP3 and rMRP3 was measured by rapid filtration technique.


RESULTS
ATP-dependent uptake of glucuronide conjugates, glutathione conjugates. and [3H]methotrexate (MTX) was stimulated by infection of cDNAs for hMRP3 and rMRP3. The mean (+/- SE) Km values for the uptake of 17beta estradiol 17beta-D-glucuronide ([3H]E(2)17 betaG) by hMRP3 and rMRP3 were 42.9 +/- 4.3 microM and 33.4 +/- 2.2 microM, respectively. Although the Ki values of glucuronides on the uptake of E217betaG were similar in humans and rats, hMRP3 exhibited higher Ki values toward MTX. In addition, although glycocholate and taurolithocholate 3-sulfate (TLC-S) were transported by both hMRP3 and rMRP3, taurocholate was only transported to a significant degree by rMRP3. Moreover, the inhibitory effect of taurocholate and glycocholate on the transport of E(2)17beta3G was much more potent in rMRP3 compared to hMRP3.


CONCLUSIONS
Collectively, the substrate specificity of hMRP3 resembles that of rMRP3 although differences were observed, particularly in bile acid transport.
Akita
Hidetaka
H
Graduate School of Pharmaceutical Sciences, The University of Tokyo, Japan.
Suzuki
Hiroshi
H
Hirohashi
Tomoko
T
Takikawa
Hajime
H
Sugiyama
Yuichi
Y
D018435:ATP Binding Cassette Transporter, Subfamily B / Q000502:physiology*; D018528:ATP-Binding Cassette Transporters / Q000502:physiology*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D016367:Baculoviridae / Q000235:genetics; D001692:Biological Transport; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D005822:Genetic Vectors; D020719:Glucuronides / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D008727:Methotrexate / Q000378:metabolism; D051381:Rats; D013379:Substrate Specificity
D018435:ATP Binding Cassette Transporter, Subfamily B; D018528:ATP-Binding Cassette Transporters; D020719:Glucuronides; D000255:Adenosine Triphosphate; C095122:multidrug resistance protein 3; D005978:Glutathione; D008727:Methotrexate