» Articles » PMID: 7077651

Further Studies on the Charge-related Alterations of Methotrexate Transport in Ehrlich Ascites Tumor Cells by Ionic Liposomes: Correlation with Liposome-cell Association

Overview
Journal J Membr Biol
Date 1982 Jan 1
PMID 7077651
Authors
Affiliations
Soon will be listed here.
Abstract

Interaction of positively (phosphatidylcholine/stearylamine 5:1) or negatively (phosphatidylcholine/stearic acid 5:1) charged liposomes with Ehrlich ascites tumor cells for 1-5 min increases or decreases, respectively, the bidirectional fluxes of the folic acid analog, methotrexate. These effects on influx and efflux appear to be symmetrical since the liposomes do not change the intracellular level of methotrexate at the steady state. Influx kinetics show that these alterations result from an increase or decrease in the Vmax with no change in the Kinm. These effects appear to be specific for the methotrexate-tetrahydrofolate carrier system since the transport of other compounds which utilize this carrier, aminopterin, 5-methyltetrahydrofolate, and 5-formyltetrahydrofolate, is affected similarly to methotrexate, whereas, the transport of folic acid, a compound similar in structure and charge but not significantly transported by this carrier is unaffected by liposomes. Once cells are exposed to charged liposomes, the effects on methotrexate transport cannot be reversed by washing the cells free of the extracellular liposomes. If, however, cells are exposed to liposomes of one charge, washed and then exposed to liposomes of the opposite charge, methotrexate influx is reversed to control rates. The effects of charged liposomes on methotrexate influx were not abolished by treating the cells with neuraminidase, metabolic inhibitors or lowering the temperature to 4 degrees C. Studies on the uptake of [14C] liposomes show that these effects are not proportional to the total amount of lipid associated with the cell but result from an initial rapid liposome-cell association that is not dependent on temperature or energy metabolism nor related to cell surface charge.

References
1.
Bouma S, Drislane F, Huestis W . Selective extraction of membrane-bound proteins by phospholipid vesicles. J Biol Chem. 1977; 252(19):6759-63. View

2.
Ozato K, Huang L, Pagano R . Interactions of phospholipid vesicles with murine lymphocytes. II. Correlation between altered surface properties and enhanced proliferative response. Membr Biochem. 1978; 1(1-2):27-42. DOI: 10.3109/09687687809064157. View

3.
KATCHALSKI E, Silman I, Goldman R . Effect of the microenvironment on the mode of action of immobilized enzymes. Adv Enzymol Relat Areas Mol Biol. 1971; 34:445-536. DOI: 10.1002/9780470122792.ch7. View

4.
Poste G, Papahadjopoulos D, Vail W . Lipid vesicles as carriers for introducing biologically active materials into cells. Methods Cell Biol. 1976; 14:33-71. DOI: 10.1016/s0091-679x(08)60468-9. View

5.
Goldman I, LICHTENSTEIN N, OLIVERIO V . Carrier-mediated transport of the folic acid analogue, methotrexate, in the L1210 leukemia cell. J Biol Chem. 1968; 243(19):5007-17. View