Evidence for three respiratory terminals in Trypanosoma cruzi epimastigotes

The respiration of T. cruzi epimastigotes was studied using KCN (1 mM) and NaN3 (5 mM) as inhibitors and glucose (33 mM) as substrate. NaN3 inhibits 18% and KCN 58% of the oxygen uptake when T. cruzi cultures enter the stationary phase. The azide-inhibition pattern closely follows endogenous respiration pattern throughout the different growth phases. Titration of the oxygen uptake with cyanide and azide, with the results treated as Dixon plots, indicated the presence of: a) one respiratory terminal sensitive to both cyanide and azide; b) another cyanide-sensitive but azide-insensitive; c) a third insensitive to both inhibitors. Ethidium bromide (5 micrograms/ml) treatment caused the disappearance of the azide-sensitive terminal in the stationary phase.