title: Hormonal alteration of methotrexate and folate polyglutamate formation in cultured hepatoma cells.
abstract: Glutamylation of the antifolate methotrexate in H35 hepatoma cells was stimulated by physiologic concentrations of insulin and dexamethasone. At saturating concentrations of the hormone a 2.7-fold stimulation could be obtained with insulin (65 nM, 16-h exposure) and a 1.8-fold stimulation with dexamethasone (100 nM, 16-h exposure). The increases in glutamylation caused by the hormones were not additive, and both were inhibited by actinomycin D and cycloheximide. N6,O2'-dibutyryl cAMP and theophylline caused a modest reduction of glutamylation in control and dexamethasone-treated cultures, but repressed the stimulation caused by insulin by approximately one-third. Enhancement of synthesis by dexamethasone and insulin was associated with increases in the tri-, tetra-, and pentaglutamate derivatives of methotrexate, with little change in intracellular methotrexate and methotrexate diglutamate. When the conversion of folinic acid into the folylpolyglutamate pool was examined in folate-depleted H35 cells, insulin and dexamethasone had similar effects. The results suggest that these hormones play a role in the glutamylation of the folate coenzymes in a liver-derived transformed cell line in culture and that these effects are also reflected in the interaction of the cells with antifolates such as methotrexate.
mesh_terms: D000818:Animals; D002460:Cell Line; D003907:Dexamethasone / Q000494:pharmacology; D005492:Folic Acid / Q000031:analogs & derivatives*; D007328:Insulin / Q000494:pharmacology; D002955:Leucovorin / Q000378:metabolism; D008114:Liver Neoplasms, Experimental / Q000378:metabolism*; D008727:Methotrexate / Q000378:metabolism*; D011624:Pteroylpolyglutamic Acids / Q000096:biosynthesis*; D051381:Rats
chemical_list: D007328:Insulin; D011624:Pteroylpolyglutamic Acids; D003907:Dexamethasone; D005492:Folic Acid; D002955:Leucovorin; D008727:Methotrexate