Table 2.
Kinetic parameters of high-affinity and low-affinity pentamidine transport in 247 and 386 procyclics
| Pentamidine |
Propamidine | Pentamidine |
|||
|---|---|---|---|---|---|
| HAPT1 Km (μM) | HAPT1 Vmax (pmol/107 cells/s) | HAPT1 Ki (μM) | LAPT1 Km (μM) | LAPT1 Vmax (pmol/107 cells/s) | |
| STIB 247WT | 0.029 ± 0.001 | 0.008 ± 0.002 | 14 ± 2 | 49 ± 19 | 0.65 ± 0.17 |
| STIB 247MR | NP | 56 ± 19 | 0.41 ± 0.10 | ||
| STIB 386WT | 0.027 ± 0.004 | 0.007 ± 0.002 | 22 ± 6 | 46 ± 9 | 0.70 ± 0.15 |
| STIB 386MR | NP | 51 ± 2 | 1.2 ± 0.4 | ||
Uptake of [3H]pentamidine by suspensions of 107 procyclic trypanosomes was measured at 25 nM or 1 μM for the determination of parameters of high-affinity transport (HAPT1 mediated) or low-affinity transport (LAPT1 mediated), respectively. In the 247MR and 386MR strains, no high-affinity pentamidine transport was observed and transport rates were very low, with saturation only at very high concentrations of unlabelled pentamidine, consistent with uptake by LAPT1. NP, not present in these cells.