ATP-dependent transport of bile salts by rat multidrug resistance-associated protein 3 (Mrp3).

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Hirohashi T, Suzuki H, Takikawa H, Sugiyama Y

ATP-dependent transport of bile salts by rat multidrug resistance-associated protein 3 (Mrp3).

J Biol Chem. 2000 Jan 28;275(4):2905-10.

PubMed ID

10644759 [ View in PubMed

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Abstract

We have previously shown that cloned rat multidrug resistance-associated protein 3 (Mrp3) has the ability to transport organic anions such as 17beta-estradiol 17-beta-D-glucuronide (E(2)17betaG) and has a different substrate specificity from MRP1 and MRP2 in that glutathione conjugates are poor substrates for Mrp3 (Hirohashi, T., Suzuki, H., and Sugiyama, Y. (1999) J. Biol. Chem. 274, 15181-15185). In the present study, the involvement of Mrp3 in the transport of endogenous bile salts was investigated using membrane vesicles from LLC-PK1 cells transfected with rat Mrp3 cDNA. The ATP-dependent uptake of [(3)H]taurocholate (TC), [(14)C]glycocholate (GC), [(3)H]taurochenodeoxycholate-3-sulfate (TCDC-S), and [(3)H]taurolithocholate-3-sulfate (TLC-S) was markedly stimulated by Mrp3 transfection in LLC-PK1 cells. The extent of Mrp3-mediated transport of bile salts was in the order, TLC-S > TCDC-S > TC > GC. The K(m) and V(max) values for the uptake of TC and TLC-S were K(m) = 15.9 +/- 4.9 microM and V(max) = 50.1 +/- 9.3 pmol/min/mg of protein and K(m) = 3.06 +/- 0.57 microM and V(max) = 161.9 +/- 21.7 pmol/min/mg of protein, respectively. At 55 nM [(3)H]E(2)17betaG and 1.2 microM [(3)H]TC, the apparent K(m) values for ATP were 1.36 and 0.66 mM, respectively. TC, GC, and TCDC-S inhibited the transport of [(3)H]E(2)17betaG and [(3)H]TC to the same extent with an apparent IC(50) of approximately 10 microM. TLC-S inhibited the uptake of [(3)H]E(2)17betaG and [(3)H]TC most potently (IC(50) of approximately 1 microM) among the bile salts examined, whereas cholate weakly inhibited the uptake (IC(50) approximately 75 microM). Although TC and GC are transported by bile salt export pump/sister of P-glycoprotein, but not by MRP2, and TCDC-S and TLC-S are transported by MRP2, but not by bile salt export pump/sister of P-glycoprotein, it was found that Mrp3 accepts all these bile salts as substrates. This information, together with the finding that MRP3 is extensively expressed on the basolateral membrane of human cholangiocytes, suggests that MRP3/Mrp3 plays a significant role in the cholehepatic circulation of bile salts.

DrugBank Data that Cites this Article

Drug Transporters

Drug	Transporter	Kind	Organism	Pharmacological Action	Actions
Cholic Acid	Canalicular multispecific organic anion transporter 2	Protein	Humans	Unknown	Inhibitor	Details
Taurocholic acid	Canalicular multispecific organic anion transporter 2	Protein	Humans	Unknown	Substrate Inhibitor	Details