Antifolate transport in L1210 leukemia cells. Kinetic evidence for the non-identity of carriers for influx and efflux.
The kinetics of methotrexate transport in L1210 cells are described. Data derived from the measurmenets of initial influx, the complete time-course of uptake, intracellular steady-state level and unidirectional efflux were found to be consistent with a simple empirical equation containing three constants. Properties of the system include the following: (1) saturability of initial influx: (2) approach to steady state during uptake is exponential; (3) the half-time for drug uptake is independent of external concentration and equal to half-time for efflux; and (4) transport is concentrative at low external concentrations, whereas the reverse is true at high external concentrations. These observations are incorporated into a kinetic model which quantitatively accounts for the data on the basis of the hypothesis that influx and efflux take place via different carriers.
D000818:Animals; D001693:Biological Transport, Active; D007700:Kinetics; D007939:Leukemia L1210 / Q000378:metabolism*; D008433:Mathematics; D008727:Methotrexate / Q000378:metabolism*; D051379:Mice; D008815:Mice, Inbred Strains; D008954:Models, Biological
D008727:Methotrexate