[Correlation between ara-C sensitivity and intracellular ara-C concentration in a cultured human lymphocyte model]

Sensitivity to cytosine arabinoside (ara-C), i.e.; the relative viable cell count on day 5 after incubation of the cell suspension (3 X 10(5) cells/ml) with 0.1 microM (2.4 ng/ml) ara-C, could be correlated with the plateau level of ara-CTP in eight out of 10 human lymphoblastic cell lines tested in vitro (correlation coefficient; r = -0.76, p less than 0.05). The plateau ara-CTP level was estimated by the incubation of the cell suspension (5 X 10(6) cells/ml) with 0.1 microM 3H-ara-C for 4 hr. The ara-CTP level was certified to be determined by the capacity for not only ara-C phosphorylation but also the ara-CTP degradation in the B-cell lines, and, in addition, by the ara-C deamination in the T-cell lines.