Mitochondrial respiratory parameters

The mitochondrial respiratory parameters have also been employed to determine the toxicity of surfactants, including anionic (LAS), nonionic (NPEO) and their metabolites, sulfophenyl carboxylates (SPCs), NP and nonylphenoxy carboxylate (NPECi) [37]. The system employed was the in vitro response of submitochondrial particles from beef heart. The EC50 toxicity calculated as the reduction rate of NAD+ ranged from 0.61 mg L-1 for a commercial LAS mixture to 18 000 mg L-1 for SPCs, and 1.3 mg L-1, 8.2 and 1.8mgL 1 for NPEOio, NPECi and NP, respectively. These results indicate that from the toxicity perspective, LAS is the compound demanding increased attention, while for NPEO, the parental compound and the metabolites must be quantified. 

Mitochondria are the powerhouse of ATP production in the cell, and through oxidative phosphorylation, are involved in approximately 90% of the ATP generated. Respiratory bursts can cause mitochondrial leakage and result in elevated levels of oxidative stress parameters, as evidenced in the microglial lesions of AD (Lassmann... 

Gianazza and co-workers have carried a series of elegant proteomic studies aimed at establishing correlations between flavin metabolism and mitochondrial flavoenzyme dysfunction (Gianazza et al. 2006). A detailed investigation was carried out on muscle mitochondria from a patient with profound muscle weakness associated with MADD. The patient received riboflavin supplementation treatment (200 mg/day) in combination with carnitine treatment (2g/day) which resulted in a substantial improvement, as assessed by biochemical parameters. Prior the therapeutic riboflavin supplementation, the activity of different fatty acid (5-oxidation enzymes, respiratory complexes, the ratio between acyl/free carnitine and the levels of intracellular lipids were altered in respect to controls. These data led the authors to evaluate the FAD and FMN concentrations in whole muscle, and the results evidenced a lower amount of available FAD upon riboflavin therapy the flavin levels were restored to, at least, control levels. 

The kinetic and equilibrium parameters of L-malate, succinate, citrate, and a-oxoglutarate uptake have been determined in mitochondria isolated from respiratory-competent cells grown under conditions of aerobic derepression, aerobic and anaerobic catabolite repression, and inhibition of mitochondrial protein synthesis, and also in mitochondria prepared from a respiratory-deficient cytoplasmic petite strain. The activity and kinetic characteristics of the systems were similar in all cases. It may be concluded that the protein components of these transport systems are coded entirely by nuclear DNA and are synthesized on the cytoplasmic ribosomes. 

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