Transport of 5-formyltetrahydrofolate into primary cultured cerebellar granule cells.
Transport of 5-formyltetrahydrofolate (5-FTHF) into primary cultured cerebellar granule cells (CGC) was studied. Uptake of 5-FTHF into CGC was saturable with K(m)=2.86 microM and V(max)=40.8 pmol/mg protein/45 min in pH 7.4 medium. Uptake of 5-FTHF in the astrocytes has a similar style in the time curve. Uptake of 5-FTHF is characterized by countertransport because adding unlabeled 5-FTHF in the medium resulted in the efflux of labeled 5-FTHF. Uptake of 5-FTHF was inhibited by the structural analogs 5-methyltetrahydrofolate, methotrexate and folic acid (K(i)=6.64, 7.69, and 19.38 microM, respectively). Uptake was significantly decreased by high concentrations of sodium azide and sodium arsenate but not by sodium cyanide. Uptake was also inhibited by p-chloromercuriphenylsulfonate and by the anions probenecid and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid. Acute exposure of the cells to ethanol (100 mM) did not affect the uptake. It is concluded that CGC have a carrier-mediated system for the uptake of 5-FTHF and other folates.
Cai
Songmin
S
Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
Horne
Donald W
DW
D000818:Animals; D000831:Animals, Newborn; D001667:Binding, Competitive; D001692:Biological Transport / Q000187:drug effects; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000378:metabolism*; D007700:Kinetics; D002955:Leucovorin / Q000031:analogs & derivatives / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D019810:Sodium Azide / Q000494:pharmacology; D012966:Sodium Cyanide / Q000494:pharmacology
D019810:Sodium Azide; D012966:Sodium Cyanide; D002955:Leucovorin