Uptake of pentamidine in Trypanosoma brucei brucei is mediated by the P2 adenosine transporter and at least one novel, unrelated transporter

Diamidine drugs such as pentamidine and berenil (diminazene aceturate) are vital drugs for the treatment of early stage human African trypanosomiasis and the corresponding veterinary condition, respectively. The action of dia midines on trypanosomes is critically dependent on their efficient uptake b y the parasite, We have therefore investigated the mode of uptake of pentam idine by Trypanosoma brucei brucei, using [I-125]iodopentamidine as a perme ant. [I-125]Iodopentamidine uptake was linear for up to 15 min and inhibite d by adenosine with a Ki value of 0.64 +/- 0.03 muM, to a maximum of 50-70% . The adenosine-sensitive flux was also inhibited by adenine with a K, valu e of 0.44 +/- 0.04 muM. Iodopentamidine uptake was saturable, with the aden osine-insensitive flux displaying a K-m of 22 +/- 2 muM and a V-max of 2.2 +/- 0.9 pmol(10(7) cells)(-1) s(-1), whereas the adenosine-sensitive flux w as inhibited by much lower iodopentamidine concentrations. These results cl early demonstrate that iodopentamidine is taken up by at least two differen t T. b. brucei transporters. an adenosine-sensitive pentamidine transporter (ASPT1) and a low-affinity pentamidine transporter (LAPT1), The identity o f these transporters was investigated, and their significance for drug upta ke and resistance in African trypanosomes is discussed. (C) 2001 Elsevier S cience B.V. All rights reserved.