Direct measurement of melphalan conjugation with glutathione: studies with human melanoma cells and mammalian liver.
The rate of formation of the major glutathione conjugate of the antitumor alkylating agent melphalan can be directly measured by high pressure liquid chromatography. Rates of melphalan-glutathione conjugate formation were determined in the presence and in the absence of human melanoma cell homogenates, or cell fractions from various tissue sources, and the relative contributions of enzyme-catalyzed and nonenzymatic conjugate formation to the overall rates of conjugation were determined. Significant rates of conjugation were observed in the absence of any enzyme-containing cell fractions. These rates were not increased by the addition of melanoma cell homogenates, animal liver microsomes or human liver cytosol or microsomes, even though these preparations all enhanced the rate of conjugation of 1-chloro-2,4-dinitrobenzene. Animal liver cytosol contains enzymes that provided a significant contribution to the overall rate of melphalan conjugate formation. We conclude that although liver cytosol contains enzymes that significantly enhance the rate of glutathione conjugation with melphalan, in the case of the tumor cells studied, cellular glutathione S-transferase-catalyzed activity appears to be, at best, a very minor determinant of the overall rate of melphalan-glutathione conjugate formation.
Guenthner
T M
TM
Department of Pharmacology, University of Illinois College of Medicine, Chicago.
Whalen
R
R
Jevtović-Todorović
V
V
D000818:Animals; D004137:Dinitrochlorobenzene / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008099:Liver / Q000378:metabolism*; D008297:Male; D008545:Melanoma / Q000378:metabolism*; D008558:Melphalan / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains; D014407:Tumor Cells, Cultured
D004137:Dinitrochlorobenzene; D005978:Glutathione; D008558:Melphalan