Sensitivity to nitrogen mustard as a function of transport activity and proliferative rate in L5178Y lymphoblasts.

natural substrate choline was also a function of the proliferative state of the cells. Transport was more efficient in log-phase cells as manifested by a higher binding affinity between carrier and each of the three substrates; in addition transport capacity for hydrolyzed HN2 and choline was significantly greater in log-phase cells than resting cells. The greater sensitivity of log-phase cells to HN2 to a large extent can be accounted for by a more efficient transport mechanism. The activity of the transport system for HN2 may be dependent upon proliferative rate, transport being more active in rapidly dividing cells.