Polyamine transport in human promyelocytic leukemia cells and polymorphonuclear leukocytes

We examined the kinetics of polyamine uptake by human myeloid cells at different stages of maturity. The Km values of putrescine, spermidine and spermine transport by HL-60 cells were 52, 7.9 and 8.1 microM, respectively. These values decreased to 5.1, 1.7 and 0.77 microM, respectively, in HL-60 cells induced to mature past the promyelocyte stage by DMSO. In human PMNs, the respective Km values were 501, 479 and 381 microM. Transport by HL-60 cells was enhanced when intracellular polyamine levels were reduced with difluoromethylornithine. Thus, HL-60 cell maturation is accompanied by an increase in the affinity of their polyamine transport system. This system is much more efficient than that found in end-stage PMNs, suggesting that it plays a more important role in supporting the metabolic requirements of HL-60 cells. Alternatively, the low affinity of the PMN polyamine transport system could represent an adaptation to the high polyamine concentrations found at infection sites.