Related Experiment Videos
[Effect of polymyxins B and M on oxygen uptake by rat liver mitochondria]
Abstract:
Polycationic peptide antibiotics, polymixins B and M, are studied for their effect on oxygen uptake by rat liver mitochondria. They both inhibit the process at state 3 and 3p according to Chance. Low concentrations of polymixin M do not affect oxygen uptake by mitochondria at state 4, but its high concentrations inhibit it. Concentration dependence of polymixin B effect on mitochondria at state 4 is of a bell-like character. Competitive interrelations are found between polymixins M and B in their effect on mitochondria at state 4. Chromatography reveals differences in peptide mobility in a thin layer. It is supposed that polymixin inhibition of oxygen uptake by mitochondria is associated with a disordering effect of the polymixins on the membrane structure during peptide binding to the lipid phase of the membranes. Low concentrations of polymixin B are likely to promote an increase in membrane permeability of mitochondria at state 4.
Insights
Polymyxins B and M antibiotics inhibit mitochondrial respiration. Polymyxins disrupt mitochondrial membranes, affecting oxygen uptake, with Polymyxin B potentially increasing membrane permeability at low doses.
Area of Science:
- Biochemistry
- Cell Biology
- Pharmacology
Background:
- Polycationic peptide antibiotics, polymixins B and M, are crucial in treating multidrug-resistant Gram-negative bacterial infections.
- Mitochondria are vital cellular organelles responsible for energy production through oxidative phosphorylation.
Purpose of the Study:
- To investigate the effects of polymixins B and M on the oxygen uptake of rat liver mitochondria.
- To elucidate the mechanism underlying polymixin-induced inhibition of mitochondrial respiration.
Main Methods:
- Measurement of mitochondrial oxygen consumption rates at different respiratory states (state 3, 3p, and 4) using a Clark-type oxygen electrode.
- Thin-layer chromatography was employed to analyze the mobility and potential differences between polymyxins B and M.
- Assessment of competitive interactions between polymixins B and M.
Main Results:
- Both polymyxins B and M significantly inhibited mitochondrial respiration at state 3 and 3p.
- Polymixin M inhibited state 4 respiration only at high concentrations, whereas polymixin B exhibited a bell-shaped concentration-dependent effect on state 4 respiration.
- Competitive interrelations were observed between polymixins B and M concerning their effects on state 4 respiration.
- Chromatographic analysis revealed distinct mobilities for polymyxins B and M.
Conclusions:
- Polymyxin inhibition of mitochondrial oxygen uptake is likely due to membrane structure disordering upon peptide binding to the lipid phase.
- Low concentrations of polymyxin B may enhance mitochondrial membrane permeability at state 4.
- Polymyxins B and M exhibit differential effects on mitochondrial respiration, suggesting distinct interaction mechanisms with the mitochondrial membrane.