Characteristics of the accumulation of methotrexate polyglutamate derivatives in Ehrlich ascites tumor cells and isolated rat hepatocytes

Journal Article · Sat Jan 01 04:00:00 EST 1983 · Adv. Exp. Med. Biol.; (United States)

DOI:https://doi.org/10.1007/978-1-4757-5241-0_17· OSTI ID:5590470

Fry, D W; Gewirtz, D A; Yalowich, J C; Goldman, I D

The intracellular synthesis and retention of polygammaglutamyl derivatives of methotrexate and their interactions with H/sub 2/ folate reductase was evaluated. Methotrexate polyglutamates were detected within 15 minutes in hepatocytes exposed to 1 microM methotrexate, and continued to accumulate for at least 60 minutes producing a large transmembrane gradient. These derivatives appeared to be preferentially retained within the cell. In studies with the Ehrlich ascites tumor accumulation of methotrexate polyglutamates was increased over 5-fold by the addition of 5 mM L-glutamine or L-glutamate and exhibited a positive correlation with the extracellular concentration of methotrexate. When Ehrlich ascites tumor cells were exposed to 10 microM methotrexate and 5 mM L-glutamine intracellular polyglutamates were detected within 10 minutes and their levels increased linearly over 4 hours. As these derivatives accumulated, there was a decline in intracellular methotrexate due at least in part to a replacement of methotrexate on H/sub 2/ folate reductase by polyglutamates and subsequent efflux of the previously bound methotrexate from the cell. When polyglutamate derivatives were in excess of the H/sub 2/ folate reductase binding capacity and extracellular methotrexate removed, methotrexate rapidly exited the cell whereas the majority of its metabolites were retained and eventually saturated the major portion of the enzyme. These studies indicate that (1) intracellular methotrexate is rapidly converted to polygammaglutamyl derivatives, (2) these metabolites effectively compete with methotrexate for binding sites on H/sub 2/ folate reductase, (3) these derivatives are retained within the cell more effectively than methotrexate, and (4) vincristine and probenecid may be potentially useful for selectively increasing methotrexate polyglutamates in tumor cells.

• Research Organization: Department of Medicine, Medical College of Virginia, Richmond
• OSTI ID: 5590470
• Journal Information: Adv. Exp. Med. Biol.; (United States), Journal Name: Adv. Exp. Med. Biol.; (United States) Vol. 163; ISSN AEMBA
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
560305 -- Chemicals Metabolism & Toxicology-- Vertebrates-- (-1987)
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ALKALOIDS
AMIDES
AMINO ACIDS
AMP
ANIMALS
ANTIMETABOLITES
ANTIMITOTIC DRUGS
AROMATICS
AZAARENES
AZOLES
BIOCHEMICAL REACTION KINETICS
CARBOXYLIC ACIDS
CELL CULTURES
DRUGS
EHRLICH ASCITES TUMOR
ENZYMES
EXPERIMENTAL NEOPLASMS
FOLIC ACID
GLUTAMINE
HEMATINICS
HEMATOLOGIC AGENTS
HETEROCYCLIC COMPOUNDS
HYDROGENASES
HYDROXY COMPOUNDS
INDOLES
KINETICS
MAMMALS
MEMBRANE TRANSPORT
METABOLISM
METABOLITES
METHOTREXATE
NUCLEOTIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
OXIDOREDUCTASES
PTERIDINES
PURINES
PYRROLES
RATS
REACTION KINETICS
RODENTS
VERTEBRATES
VINBLASTINE
VITAMIN B GROUP
VITAMINS
XANTHINES