Tricarboxylic acid cycle operation at the kinetoplast-mitochondrion complex of Trypanosoma cruzi

Abstract

Culture of Trypanosoma cruzi (Tulahuen strain) in the presence of ethidium bromide (1–20 μg/ml) resulted in dyskinetoplasty and inhibition of growth, to an extent depending on the dye concentration and the medium composition. The ethidium bromide-induced dyskinetoplasty caused a decrease of (a) the cytochrome content of epimastigotes ( a,a 3 and b species); (b) the rate of respiration (endogenous or supported by D-glucose); and (c) the rate of production of 14CO 2 from [2- 14C]acetate and [1- 14C]glucose. [2- 14C]Acetate oxidation to 14CO 2 was affected by dyskinetoplasty more than [1- 14C]glucose oxidation, particularly at the exponential growth phase. With dyskinetoplastic epimastigotes, diminution of 14CO 2 production from [2- 14C]acetate largely exceeded that of oxygen uptake, while with [1- 14C]glucose, 14CO 2production and respiration were affected to about the same extent. Dyskinetoplasty also decreased the incorporation of [2- 14C]acetate carbon into intermediates of the tricarboxylic acid cycle and related amino acids, and modified the distribution pattern of 14C in accordance with the decrease of respiration. Reduction of cytochrome content of epimastigotes by restriction of heme compounds during growth decreased 14CO 2 production from [2- 14C]acetate, like the ethidium-induced dyskinetoplasty. The same occurred after inhibition of electron transfer by antimycin and cyanide, though to a much more significant extent, thus confirming the functional association of electron transport at the mitochondrial cytochrome system of T. cruzi and the enzymatic reactions of the tricarboxylic acid cycle.