Isolation and characterization of a CHO amino acid transport mutant resistant to melphalan (L-phenylalanine mustard).
A mutant of Chinese hamster ovary cells, CHY-2, was isolated on the basis of its reduced ability to grow on a limiting concentration of leucine and was found to be defective in uptake of leucine via the sodium-independent L system. Consistent with published reports that the L system can mediate melphalan uptake, the D10 of the mutant for melphalan was increased threefold under conditions designed to limit drug uptake to the L system (brief exposure in sodium-free medium). Unlike a previously described melphalan-resistant CHO mutant (CHr), CHY-2 displays no cross-resistance to colchicine or puromycin. It differs from a second melphalan-resistant CHO mutant, melr, in its sensitivity to melphalan in the presence of high Na+, and from a melphalan-resistant mouse leukemic cell in possessing normal levels of intracellular glutathione. Thus, CHY-2 represents a new melphalan-resistant mutant class. The effect of the CHY-2 mutation is pleiotropic, involving significant reductions in amino acid uptake via the L, A and Ly+ (but not ASC) systems. The primary defect is unknown; however, the mutant possesses normal intracellular concentrations of Na+ and K+ and normal membrane fluidity. The growth rate of the mutant in standard medium is greatly reduced (generation time of 60 h vs. 24 h), although it can be improved by the addition of a supplement containing high concentrations of leucine, proline, and peptides.
D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D004351:Drug Resistance; D005260:Female; D005978:Glutathione / Q000378:metabolism; D007700:Kinetics; D007930:Leucine / Q000378:metabolism*; D008558:Melphalan / Q000633:toxicity*; D009154:Mutation; D010053:Ovary
D000596:Amino Acids; D005978:Glutathione; D007930:Leucine; D008558:Melphalan