Mouse P388 and
L1210 leukemia cells grown in vitro were found to be 4 to 10 times more sensitive to
6-diazo-5-oxo-L-norleucine and 3 to 5 times more sensitive to
Acivicin than were 3T3 and C57BL x DBA/2 F1 embryonic fibroblasts. The combined actions of succinylated Acinetobacter
glutaminase-asparaginase and
6-diazo-5-oxo-L-norleucine or
Acivicin produced synergistic inhibition of
nucleic acid synthesis in P388
tumor cells. An uptake system for
Acivicin is described. Its properties in P388 and 3T3 cells are similar in their strong temperature dependence, utilization of the "L" transport system, presumably competitive inhibition by
glutamine, similar Km's (about 200 microM), and potent inhibition by p-chloromercuribenzene sulfonate, NA+. However,
Acivicin uptake was inhibited in 3T3 (but not in P388) cells by KCN or
2,4-dinitrophenol. At equilibrium in P388 cells, the intracellular level of
Acivicin was approximately 57-fold greater than was the extracellular concentration. The accumulated
Acivicin was not metabolized by P388 cells, nor does exchange of 3H label into water occur. Rapid efflux of
Acivicin occurred with both cell lines at 37 degrees, but efflux from 3T3 cells was greatly diminished at 0 degrees. The rate of efflux was accelerated by including
glutamine or unlabeled
Acivicin in the extracellular medium.