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Pharmacokinetic Imaging Using Tc-99m-Mebrofenin to Untangle the Pattern of Hepatocyte Transporter Disruptions Induced by Endotoxemia in Rats
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International audience. Endotoxemia-induced inflammation may impact the activity of hepatocyte transporters, which control the hepatobiliary elimination of drugs and bile acids. Tc-99m-mebrofenin is a nonmetabolized substrate of transporters expressed at the different poles of hepatocytes. Tc-99m-mebrofenin imaging was performed in rats after the injection of lipopolysaccharide (LPS). Changes in transporter expression were assessed using quantitative polymerase chain reaction of resected liver samples. Moreover, the particular impact of pharmacokinetic drug-drug interactions in the context of endotoxemia was investigated using rifampicin (40 mg/kg), a potent inhibitor of hepatocyte transporters. LPS increased Tc-99m-mebrofenin exposure in the liver (1.7 +/- 0.4-fold). Kinetic modeling revealed that endotoxemia did not impact the blood-to-liver uptake of Tc-99m-mebrofenin, which is mediated by organic anion-transporting polypeptide (Oatp) transporters. However, liver-to-bile and liver-to-blood efflux rates were dramatically decreased, leading to liver accumulation. The transcriptomic profile of hepatocyte transporters consistently showed a downregulation of multidrug resistance-associated proteins 2 and 3 (Mrp2 and Mrp3), which mediate the canalicular and sinusoidal efflux of Tc-99m-mebrofenin in hepatocytes, respectively. Rifampicin effectively blocked both the Oatp-mediated influx and the Mrp2/3-related efflux of Tc-99m-mebrofenin. The additive impact of endotoxemia and rifampicin led to a 3.0 +/- 1.3-fold increase in blood exposure compared with healthy non-treated animals. Tc-99m-mebrofenin imaging is useful to investigate disease-associated change in hepatocyte transporter function.
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