Fig. 2

Uptake of 5-[¹⁴C]-Methyl-THF in the liver BLMV as a function of substrate concentration, structural analogs, and binding of 5-[¹⁴C]-Methyl-THF to liver BLM. a Uptake was measured by varying 5-[¹⁴C]-Methyl-THF concentration from 0.125 to 8.0 μM in the incubation medium (100 mM NaCl, 80 mM mannitol, 10 mM HEPES, 10 mM 2-morpholinoethanesulfonic acid (MES), pH 5.5) after incubating liver BLMV for 10 s. b Effect of structural analog and inhibitors on the uptake of 5-[¹⁴C]-Methyl-THF in the liver BLMV. Uptake of 5-[¹⁴C]-Methyl-THF (0.5 μM) was measured with and without analogs (5 μM folic acid and 5 μM methotrexate)/inhibitor (5 mM thymine pyrophosphate (TPP) and 25 μM hemin) in incubation buffer of pH 5.5. Bars are mean ± SD of 4 separate uptake determinations. c Binding of 5-[¹⁴C]-Methyl-THF to liver BLM and the contribution of transporters to folate binding. Binding of 5-[¹⁴C]-Methyl-THF (0.5 μM) was determined by incubating liver BLMV at 4 °C in the binding buffer (100 mM NaCl, 80 mM mannitol, 10 mM HEPES, 10 mM MES, pH 5.5) for 10 s, and the binding of 5-[¹⁴C]-Methyl-THF (0.5 μM) to liver BLM was measured in presence and absence of structural analogs (5 μM folic acid and 5 μM methotrexate)/inhibitor (5 mM thymine pyrophosphate (TPP) AND 25 μM hemin) in incubation buffer of pH 5.5. Each data point is mean ± SD of 4 separate binding determinations. *p < 0.05; **p < 0.01; ***p < 0.001 versus control and ^# p < 0.05; ^## p < 0.01; ^### p < 0.001 versus none