Identification of glutathione as a driving force and leukotriene C4 as a substrate for oatp1, the hepatic sinusoidal organic solute transporter.

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Li L, Lee TK, Meier PJ, Ballatori N

Identification of glutathione as a driving force and leukotriene C4 as a substrate for oatp1, the hepatic sinusoidal organic solute transporter.

J Biol Chem. 1998 Jun 26;273(26):16184-91.

PubMed ID

9632674 [ View in PubMed

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Abstract

oatp1 is an hepatic sinusoidal organic anion transporter that mediates uptake of various structurally unrelated organic compounds from blood. The driving force for uptake on oatp1 has not been identified, although a role for bicarbonate has recently been proposed. The present study examined whether oatp1-mediated uptake is energized by efflux (countertransport) of intracellular reduced glutathione (GSH), and whether hydrophobic glutathione S-conjugates such as leukotriene C4 (LTC4) and S-dinitrophenyl glutathione (DNP-SG) form a novel class of substrates for oatp1. Xenopus laevis oocytes injected with the complementary RNA for oapt1 demonstrated higher uptake of 10 nM [3H]LTC4 and 50 microM [3H]DNP-SG, and higher efflux of [3H]GSH (2.5 mM endogenous intracellular GSH concentration). The oatp1-stimulated LTC4 and DNP-SG uptake was independent of the Na+ gradient, cis-inhibited by known substrates of this transport protein and by 1 mM GSH, and was saturable, with apparent Km values of 0.27 +/- 0.06 and 408 +/- 95 microM, respectively. Uptake of [3H]taurocholate, an endogenous substrate of oatp1, was competitively inhibited by DNP-SG. Of significance, oatp1-mediated taurocholate and LTC4 uptake was cis-inhibited and trans-stimulated by GSH, and [3H]GSH efflux was enhanced in the presence of extracellular taurocholate or sulfobromophthalein, indicating that GSH efflux down its large electrochemical gradient provides the driving force for uptake via oatp1. The stoichiometry of GSH/taurocholate exchange was 1:1. These findings identify a new class of substrates for oatp1 and provide evidence for GSH-dependent oatp1-mediated substrate transport.

DrugBank Data that Cites this Article

Drug Transporters

Drug	Transporter	Kind	Organism	Pharmacological Action	Actions
Ouabain	Solute carrier organic anion transporter family member 1A2	Protein	Humans	Unknown	Substrate Inhibitor	Details
Taurocholic acid	Solute carrier organic anion transporter family member 1A2	Protein	Humans	Unknown	Substrate Inhibitor Inducer	Details