Influence of Cation Transporters (OCTs and MATEs) on the Renal and Hepatobiliary Disposition of [ 11 C]Metoclopramide in Mice.

Purpose: To investigate the role of cation transporters (OCTs, MATEs) in the renal and hepatic disposition of the radiolabeled antiemetic drug [ ¹¹ C]metoclopramide in mice with PET.
Methods: PET was performed in wild-type mice after administration of an intravenous microdose (<1 μg) of [ ¹¹ C]metoclopramide without and with co-administration of either unlabeled metoclopramide (5 or 10 mg/kg) or the prototypical cation transporter inhibitors cimetidine (150 mg/kg) or sulpiride (25 mg/kg). [ ¹¹ C]Metoclopramide PET was also performed in wild-type and Slc22a1/2 ^(-/-) mice. Radiolabeled metabolites were measured at 15 min after radiotracer injection and PET data were corrected for radiolabeled metabolites.
Results: [ ¹¹ C]Metoclopramide was highly metabolized and [ ¹¹ C]metoclopramide-derived radioactivity was excreted into the urine. The different investigated treatments decreased (~2.5-fold) the uptake of [ ¹¹ C]metoclopramide from plasma into the kidney and liver, inhibited metabolism and decreased (up to 3.8-fold) urinary excretion, which resulted in increased plasma concentrations of [ ¹¹ C]metoclopramide. Kidney and liver uptake were moderately (~1.3-fold) reduced in Slc22a1/2 ^(-/-) mice.
Conclusions: Our results suggest a contribution of OCT1/2 to the kidney and liver uptake and of MATEs to the urinary excretion of [ ¹¹ C]metoclopramide in mice. Cation transporters may contribute, next to variability in the activity of metabolizing enzymes, to variability in metoclopramide pharmacokinetics and side effects.