This report describes a potent and selective inhibitor of multidrug and toxin extrusion (MATE) protein, pyrimethamine (PYR), and examines its effect on the urinary and biliary excretion of typical Mate1 substrates in mice. In vitro inhibition studies demonstrated that PYR is a potent inhibitor of mouse (m)Mate1 (K_i = 145 nM) among renal organic cation transporters mOctn1 and mOctn2 (K_i > 30 μM), mOct1 (K_i = 3.6 μM), and mOct2 (K_i = 6.0 μM). PYR inhibited the uptake of metformin by kidney brush-border membrane vesicles (BBMVs) (K_i = 41 nM) and canalicular membrane vesicles in the presence of outward gradient of H⁺. PYR treatment significantly increased the kidney-to-plasma ratio of tetraethylammonium, and both the liver- and kidney-to-plasma ratios of metformin in mice, whereas it did not affect their plasma concentrations and urinary excretion rates. Furthermore, the plasma lactate concentration, a biomarker for inhibition of gluconeogenesis by metformin, was significantly higher in the PYR-treated group than in the control group. These results not only suggest the importance of mMate1 in the efflux of organic cations into the urine and bile in mice but also the importance of canalicular efflux mediated by MATE proteins for the therapeutic efficacy of metformin. PYR is a potent inhibitor of human (h)MATE1 and hMATE2-K (K_i = 77 and 46 nM, respectively) and H⁺ and organic cation exchanger in human kidney BBMVs (K_i = 31 nM) in the presence of outward gradient of H⁺. Taken together, PYR can be used as a potent probe inhibitor of human MATE transporters.

We determined the impact of the extent of regional lymphadenectomy on survival in patients with urothelial carcinoma of the upper urinary tract. Between January 1989 and January 2006, 169 patients with nonmetastatic urothelial carcinoma of the upper urinary tract underwent curative surgery. We previously reported the primary sites of nodal metastases in urothelial carcinoma of the upper urinary tract. Nodal sites where the incidence of metastases was 30% or more were considered regional lymph nodes. When all primary sites were resected, this was considered complete lymphadenectomy. Regional lymphadenectomy without the removal of all primary sites was considered incomplete lymphadenectomy. We retrospectively analyzed the influence of the extent of lymphadenectomy on patient survival. A total of 45 patients (26.6%) underwent complete lymphadenectomy. Lymphadenectomy was performed in an additional 36 patients (21.3%) but it was incomplete. Lymphadenectomy was not performed in 88 patients. Cancer specific survival did not significantly differ between the groups when all patients were analyzed. However, patient survival significantly depended on the extent of lymphadenectomy when we focused on patients with T stage pT3 or higher. Patient survival was likely to improve when the number of lymph nodes removed increased. Multivariate analysis showed that complete lymphadenectomy was a significant prognostic factor for cancer specific survival (p = 0.009) as well as T stage (pT3 or less p = 0.0004) and tumor grade (G3 p = 0.0001). Although further investigation is required to make a definite conclusion, the extent of lymphadenectomy may significantly influence its therapeutic effect, especially for patients with advanced disease.

The present study investigated prediction of the overall renal tubular secretion and hepatic clearances of anionic drugs based on in vitro transport studies. The saturable uptake of eight drugs, most of which were OAT3 substrates (rosuvastatin, pravastatin, pitavastatin, valsartan, olmesartan, trichlormethiazide, p-aminohippurate, and benzylpenicillin) by freshly prepared human kidney slices underestimated the overall intrinsic clearance of the tubular secretion; therefore, a scaling factor of 10 was required for in vitro-in vivo extrapolation. We examined the effect of gemfibrozil and its metabolites, gemfibrozil glucuronide and the carboxylic metabolite, gemfibrozil M3, on pravastatin uptake by human kidney slices. The inhibition study using human kidney slices suggests that OAT3 plays a predominant role in the renal uptake of pravastatin. Comparison of unbound concentrations and K_i values (1.5, 9.1, and 4.0 μM, for gemfibrozil, gemfibrozil glucuronide, and gemfibrozil M3, respectively) suggests that the mechanism of the interaction is due mainly to inhibition by gemfibrozil and gemfibrozil glucuronide. Furthermore, extrapolation of saturable uptake by cryopreserved human hepatocytes predicts clearance comparable with the observed hepatic clearance although fluvastatin and rosuvastatin required a scaling factor of 11 and 6.9, respectively. This study suggests that in vitro uptake assays using human kidney slices and hepatocytes provide a good prediction of the overall tubular secretion and hepatic clearances of anionic drugs and renal drug-drug interactions. It is also recommended that in vitro-in vivo extrapolation be performed in animals to obtain more reliable prediction.