Polyamine and pentamidine metabolism in African trypanosomes.
A pentamidine-resistant line of bloodstream Trypanosoma brucei brucei (S427/118) has been developed by stepwise selection in axenic culture in vitro. After 57 days of selection, the resistant line (S427/118/PR32) was able to grow normally in 32 ng/ml (54 pM) pentamidine with an IC50 value of 105 ng/ml (177 pM), which is 26-times higher than that of the parental strain. Post-mitochondrial supernatant extracts of both strains were unable to metabolize [3H]pentamidine, whereas under identical conditions rat liver microsomes were able to convert > 5% of the drug to hydroxylation products. Thus metabolic conversion of pentamidine does not appear to be involved in either the mode of action of or resistance to pentamidine. Pentamidine-sensitive trypanosomes exposed for 4 h in vivo to therapeutic doses of pentamidine (4 mg/kg) did not show any significant changes in either polyamine-, thiol- or S-adenosylmethionine metabolites, indicating that inhibition of S-adenosylmethionine decarboxylase is not involved in the trypanocidal action of the drug. However, a marked increase in basic amino acid content was noted. In particular, lysine content was increased 13-fold following exposure to pentamidine.
Berger
B J
BJ
Department of Medical Parasitology, London School of Hygiene and Tropical Medicine, UK.
Carter
N S
NS
Fairlamb
A H
AH
D000818:Animals; D004351:Drug Resistance; D008862:Microsomes, Liver / Q000378:metabolism; D010419:Pentamidine / Q000378:metabolism* / Q000494:pharmacology; D011073:Polyamines / Q000378:metabolism*; D051381:Rats; D014346:Trypanosoma brucei brucei / Q000378:metabolism*; D014353:Trypanosomiasis, African / Q000378:metabolism*
D011073:Polyamines; D010419:Pentamidine