title: Effects of folinic acid on hepatoma cells containing methotrexate polyglutamates.
abstract: The effects of folinic acid on a toxic pulse exposure of cultured hepatoma cells to methotrexate (4-amino-10-methylpteroylglutamic acid) is reported. Inclusion of folinic acid (5-formyl-5,6,7,8-tetrahydropteroylglutamic acid) (10 micro M) with the 2-hr pulse of methotrexate (10 micro M) nearly completely prevents the uptake and gamma-glutamylation of methotrexate and prevents toxicity. Addition of folinic acid after methotrexate results in a partial rescue that is time and concentration dependent. Restoration of cell growth in the presence of increasing amounts of folinic acid is accompanied by a concentration-dependent elevation in tritium release from [5-3H]deoxyuridine. In the absence of folinic acid, the release of tritium from [5-3H]deoxyuridine remains inhibited for three days after exposure to methotrexate, which can be related to the cellular formation and retention of methotrexate polyglutamates. Following the 2-hr pulse of methotrexate, the cellular pool consists of 70% polyglutamates of which the predominant species has three glutamate residues (4-NH2-10-CH3PteGlu3). When methotrexate is removed from medium, following the pulse, unmetabolized methotrexate rapidly leaves the cells, and 4-NH2-10-CH3PteGlu3 is converted to methotrexate polyglutamates containing four to six glutamate residues. Addition of folinic acid after the methotrexate pulse prevents the conversion of 4-NH2-10-CH3PteGlu3 to the higher-chain-length derivatives and causes a reduction in the total methotrexate cell pools over the next 48 hr. These results suggest that the effects of folinic acid on methotrexate polyglutamates may play a role in the rescue of cells containing these derivatives.
mesh_terms: D000818:Animals; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D007700:Kinetics; D002955:Leucovorin / Q000627:therapeutic use*; D008114:Liver Neoplasms, Experimental / Q000188:drug therapy* / Q000503:physiopathology; D008727:Methotrexate / Q000031:analogs & derivatives* / Q000378:metabolism / Q000627:therapeutic use; D010455:Peptides / Q000627:therapeutic use*; D011099:Polyglutamic Acid / Q000031:analogs & derivatives / Q000378:metabolism / Q000627:therapeutic use*; D051381:Rats
chemical_list: D010455:Peptides; D011099:Polyglutamic Acid; C014085:methotrexate polyglutamate; D002955:Leucovorin; D008727:Methotrexate