Interaction of Human Organic Anion Transporters 2 and 4 with Organic Anion Transport Inhibitors

Abstract

The organic anion transport system is involved in the tubular excretion and reabsorption of various drugs and substances. The purpose of this study was to characterize the effects of various organic anion transport inhibitors on renal organic anion transport using proximal tubule cells stably expressing human organic anion transporter 2 (hOAT2) and hOAT4. Immunohistochemical analysis revealed that hOAT2 is localized to the basolateral side of the proximal tubule in the kidney. hOAT2 mediated a time-and concentration-dependent increase in prostaglandin F 2␣ (PGF 2␣ ) uptake. The organic anion transport inhibitors used for this study were probenecid, 8-(noradamantan-3-yl)-1,3-dipropylxanthine (KW-3902), betamipron, and cilastatin. Probenecid, but not KW-3902, betamipron, and cilastatin, significantly inhibited hOAT2-mediated PGF 2␣ uptake. In contrast, probenecid, KW-3902, and betamipron, but not cilastatin, inhibited hOAT4-mediated estrone sulfate (ES) uptake. Kinetic analyses revealed that these inhibitions were competitive. The K i value of probenecid for hOAT2 was 766 M, whereas those of probenecid, KW-3902, and betamipron for hOAT4 were 54.9, 20.7, and 502 M, respectively. These results suggest that probenecid, KW-3902, and betamipron could inhibit hOAT4-mediated ES uptake in vitro, whereas probenecid alone could inhibit the hOAT2-mediated PGF 2␣ uptake. Comparing the K i values with the therapeutically relevant concentrations of unbound inhibitors in the plasma, probenecid alone was predicted to inhibit hOAT4-mediated organic anion transport in vivo.Various organic anion transport inhibitors are used experimentally and clinically. Probenecid is a conventional and standard organic anion transport inhibitor experimentally, but it is used as a uricosuric drug clinically. In addition, KW-3902, developed as an adenosine A1 receptor antagonist , was also shown to inhibit organic anion transport in the basolateral membrane of opossum kidney cells derived from the American opossum kidney (Nagai et al., 1999). On the other hand, betamipron and cilastatin are administered in combination with carbapenem antibiotics, panipenem, and imipenem, respectively (Birnbaum et al., 1985;Shiba et al., 1991). Betamipron inhibits the uptake of panipenem and imipenem into proximal tubule cells (Hirouchi et al., 1994). On the other hand, imipenem is degraded by human renal dehydropeptidase-I and therefore must be administered in combination with cilastatin, a dehydropeptidase-I inhibitor, to prevent loss of antimicrobial activity in urine and limit potential nephrotoxicity associated with renal metabolism (Craig, 1997).In our previous study, we elucidated the interaction of human organic anion transporter 1 (hOAT1) and hOAT3 with organic anion transport inhibitors including probenecid, KW-3902, betamipron, and cilastatin (Takeda et al., 2001). Thus, the purpose of this study was to characterize the interaction of hOAT2 and hOAT4 with these organic anion transport inhibitors using cells derived from the second portion of the pr...

Novel liver-specific organic anion transporter OAT7 that operates the exchange of sulfate conjugates for short chain fatty acid butyrate

“…Importantly, OAT7-mediated ES uptake was not affected by probenecid, a representative inhibitor of organic anion transport. 33,34 Figure 5A also illustrates that OAT7 failed to interact with substrates of organic cation transporters, tetraethylammonium, and choline. 35 These results demonstrate that OAT7 does not encompass broad substrate specificity, which is distinct from previously cloned OAT/organic cation transporters or OATPs.…”

Expression of Organic Anion Transporter 2 in the Human Kidney and Its Potential Role in the Tubular Secretion of Guanine-Containing Antiviral Drugs

“…In addition, drug interactions and adverse drug reactions have been suggested to occur at the level of these transporters (Giacomini et al, 2010). In contrast, there is only limited evidence for the expression of OAT2 protein in the human kidney (Enomoto et al, 2002), and its role in renal tubular handling of drugs and toxins is unknown.…”

EZH2 Inhibitor GSK126: Metabolism, drug transporter and rat pharmacokinetic studies

“…Uptake experiments were performed as previously described (Hosoyamada et al, 1996;Enomoto et al, 2002;Kimura et al, 2002;Takeda et al, 2002). The S2-cells were seeded into 24-well tissue culture plates at a density of 1.0 × 10 5 cells/well.…”