Effect of Methotrexate Treatment on Expression Levels of Organic Anion Transporter Polypeptide 2, P-Glycoprotein and Bile Salt Export Pump in Rats(Pharmacology)

High-dose methotrexate (HDMTX) chemotherapy with leucovorin (LV) rescue has been used as a therapeutic strategy in oncology since the 1970s. Adverse reactions following extension of methotrexate (MTX) elimination are a crucial problem in HDMTX chemotherapy. MTX is a substrate for drug transporters, which are multidrug resistance protein 2 (Mrp2), organic anion transporter polypeptide 2 (Oatp2) and other transporters. We previously reported that MTX treatment downregulated the expression level of Mrp2 in rats. Here we examined the effect of MTX treatment on the expression of Oatp2, P-glycoprotein (P-gp) and bile salt export pump (Bsep) in rats. MTX was single-injected intraperitoneally at a dose of 150mg/kg, and Western blot analysis was performed. The levels of Oatp2, P-gp and Bsep in the liver on day 4 after treatment were downregulated to 36.3±6.9%, 51.5±5.2% and 61.8±5.5% (mean±S.E.M.) of controls, respectively. Expression levels of P-gp in the kidney and ileum were also downregulated to 38.5±1.6% and 16.2±1.6% of controls, respectively. These effects of MTX were partially recovered by LV, which rescues normal cells from MTX toxicity. In conclusion, the result indicates that MTX treatment downregulates expression levels of Oatp2, P-gp and Bsep.