Respiration and energy conservation in the filarial worm Litomosoides carinii.

The average rate of endogenous respiration of intact Litomosoides carinii was 2.24 muatom O min-1 g-1 worm wet wt. No significant difference was observed in respiration capacities between male and female worms. Rates of oxygen uptake decreased progressively during disruption and fractionation of the parasite tissue and very few respiration capabilities remained in the mitochondrial fraction. Added substrates increased the respiratory rates of the intact filariid and cell-free extracts by a factor of 1.4 to 2.3, depending on the tissue system and substrate species used. Rotenone and cyanide strongly inhibited respiration in all incubations, whereas antimycin A, in most cases, suppressed oxygen consumption only partially. ATP conservation in cell-free extracts of L. carinii, as determined by the incorporation of 32Pi into the organic phosphate fraction, was twice as high in the presence of air as under an atmosphere of nitrogen. Anaerobically, rates of phosphorylation in these extracts were similar to the amounts of lactate. Phosphorylation in mitochondria isolated from the filarial worm was supported by malate, succinate, pyruvate and TMPD/ascorbate, whereas L-glutamate and beta-hydroxybutyrate exhibited only little or no effect, respectively. P/O ratios for pyruvate-supported oxidative phosphorylation were found to approach a value of 3. Electron transport inhibitors, oligomycin and 2,4-dinitrophenol strongly inhibited substrate-dependent mitochondrial phosphorylation. The data of the present investigation, together with other recent findings made by the same authors, have provided evidence that in L. carinii mitochondria a mammalian-type of respiratory system capable of carrying out oxidative phosphorylation is functional. It seems likely that this respiration-dependent chemical energy, proceeding in addition to that generated through fermentation processes, may be vital for muscular contraction and survival of this filarial parasite.