Article Figures & Data
Figures
- FIG. 1.
Uptake of [3H]adenosine by the tbat1-null mutant. Uptake of 20 nM [3H]adenosine was inhibited by inosine (filled squares) with an IC50 of 1.1 ± 0.1 μM. Adenine failed to inhibit [3H]adenosine at concentrations as high as 100 μM when it was added alone (open squares). The inhibition induced by 1 mM adenine is attributable to a low-affinity inhibition of P1.
- FIG. 2.
Uptake of [3H]pentamidine by the tbat1-null mutant. The uptake of 15 nM [3H]pentamidine was unaffected by as much as 1 mM adenosine (filled circles) but was inhibited to a maximum of 64% by propamidine (open squares), with an IC50 of 6.5 μM. When increasing amounts of unlabeled pentamidine (filled squares) were added, [3H]pentamidine uptake was inhibited in a biphasic manner (P < 0.0001 by the F test), with the high-affinity component (IC50 = 25.1 nM) contributing 62% of total [3H] pentamidine transport. The IC50 of the low-affinity component was 19.5 μM for this experiment.
- FIG. 3.
In vitro sensitivities of bloodstream-form trypanosomes to arsenical trypanocides. (a) Wild-type T. b. brucei s427 parasites were incubated with or without 10 μM melarsen oxide in the presence of potential inhibitors. Traces: a, control (no arsenical); b, melarsen oxide only; c, melarsen oxide plus 4 mM adenosine; d, melarsen oxide plus 1 mM pentamidine; e, melarsen oxide plus 4 mM hypoxanthine. (b) Cells of the tbat1-null mutant were incubated with or without 10 μM cymelarsan. Traces: a, control (no arsenical); b, cymelarsan only; c, cymelarsan plus 0.1 μM pentamidine; d, cymelarsan plus 0.03 μM pentamidine; e, cymelarsan plus 0.01 μM pentamidine; f, cymelarsan plus 10 μM stilbamidine; g, cymelarsan plus 1 μM propamidine; h, cymelarsan plus 0.3 μM propamidine; i, cymelarsan plus 0.1 μM propamidine. (c) Cells of the tbat1-null mutant were incubated with or without 0.5 μM phenylarsine oxide. Traces: a, control (no arsenical); b, phenylarsine oxide only; c, phenylarsine oxide plus 10 mM adenosine; d, phenylarsine oxide plus 4 mM hypoxanthine; e, phenylarsine oxide plus 1 mM pentamidine; f, phenylarsine oxide plus 100 μM pentamidine; g, phenylarsine oxide plus 100 μM propamidine; h, phenylarsine oxide plus 100 μM stilbamidine. Arrow indicates time of phenylarsine oxide addition.
Tables
- TABLE 1.
Drug resistance phenotype of the tbat1-null mutant compared to the parental wild-type strain
Drug IC50a (ng/ml) Resistance factor Wild type TbAT1−/− mutant Melarsoprol 21 ± 3 49 ± 9 2.3 Melarsen oxide 3.7 ± 0.1 11 ± 0.1 3.0 Cymelarsan 6.1 ± 1 12 ± 3 2.0 Pentamidine 5.1 ± 2 12 ± 3 2.4 Diminazene 120 ± 30 2,300 ± 500 19 Propamidine 67 ± 7 750 ± 20 11 Stilbamidine 680 ± 70 5,000 ± 1,300 7.4 ↵ a IC50 were determined in vitro by using the Alamar Blue assay. Values are means from at least three independent experiments ± standard errors.
