Abstract
The active transport of folic acid (FA) 5-methyltetrahydrofolate (5-MeFH4) and methotrexate (MTX) was investigated in mouse leukemia L 1210 and in a human lymphoid cultured cell line. In both cell types exist two different transport systems, one for 5-MeFH4 which transports also MTX and one for FA which is much less effective. The first system can be inhibited by blocking sulfhydryl groups in the membrane with organic mercurial compounds. But no SH-groups seem to be involved in the transport of FA. Iodoacetate, however, leads to an increased total uptake of MTX. Resistance to MTX can be due to decreased uptake of the folate antagonist. A cell strain with impaired transport of MTX takes also up less 5-MeFH4, where as the transport of FA is not decreased. Competition experiments show that folinic acid shares the transport system with MTX and 5-MeFH4. This system seems to be the important pathway for the uptake of folate and antifolate compounds into these cells, while FA is probably taken up by a much less specific system.
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Niethammer, D., Kleihauer, E. Transport of folate compounds through the membrane of normal and transport-deficient lymphoid cells. Pediatr Res 8, 901 (1974). https://doi.org/10.1203/00006450-197411000-00038
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DOI: https://doi.org/10.1203/00006450-197411000-00038