Comparison of methotrexate polyglutamylation in L1210 leukemia cells when influx is mediated by the reduced folate carrier or the folate receptor. Lack of evidence for influx route-specific effects.

摘要: Abstract We previously described a methotrexate-resistant L1210 cell line (MTX r A) that lacks functional reduced folate carrier and does not appreciably express the receptor. In present study, we utilized MTX A lines stably transfected with cDNAs encoding either receptor or to investigate influence of route influx on rate extent methotrexate polyglutamylation. At an extracellular concentration 0.1 μM, in transfectant A-TF1) A-R1) was equal polyglutamates accumulated at identical rate, but onset delayed until dihydrofolate reductase saturated monoglutamate (~3 hr). The polyglutamate formation immediate among cells pretreated lipophilic inhibitor trimetrexate block binding reductase. spectra individual were similar, tetraglutamate as predominant form. 100-fold higher required detect uptake polyglutamylation transport defective parent line, demonstrating diffusion unidentified low affinity also supports Since achieve nearly rates despite very different mechanisms delivery, data suggest transport-mediated substrate channeling folylpolyglutamate synthetase is unlikely play role tetrahydrofolate metabolism. This study notion it intracellular achieved within drives irrespective its entry.