title: Uptake of oxidized folates by rat liver mitochondria.
abstract: Folate, dihydrofolate, and methotrexate are rapidly taken up by rat liver mitochondria. The apparent maximal matrix folate concentration is about 2.5-fold that of the suspending medium, whereas dihydrofolate and methotrexate equilibrate across the inner membrane. Fully reduced folates, including tetrahydrofolate, 5-methyltetrahydrofolate, and 5,10-methylenetetrahydrofolate penetrate only the intermembrane space. Addition of dihydrofolate or methotrexate effects a rapid release of pre-loaded folate, and external methotrexate promotes the release of pre-loaded dihydrofolate. The extent of dihydrofolate uptake is enhanced by addition of folate. These results suggest that oxidized folates are transported to the matrix by a carrier-mediated mechanism.
mesh_terms: D000818:Animals; D001692:Biological Transport; D005492:Folic Acid / Q000031:analogs & derivatives* / Q000378:metabolism*; D007425:Intracellular Membranes / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008727:Methotrexate / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000378:metabolism*; D010084:Oxidation-Reduction; D051381:Rats; D013329:Structure-Activity Relationship
chemical_list: C010920:dihydrofolate; D005492:Folic Acid; D008727:Methotrexate