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Effect of aflatoxins on oxidative phosphorylation by rat liver mitochondria
Abstract:
The in vitro effect of aflatoxins M1, B1 and G1 on oxidative phosphorylation by rat liver mitochondria with succinate as substrate has been studied. All these toxins inhibit the electron transport chain at a 1-10-4 M concentration and the site of inhibition is between cytochrome b and cytochrome c or c1. Aflatoxin M1 (AFM1) uncouples oxidative phosphorylation at a concentration of 1-10-6 M and reduces the ADP:O ratio, whereas aflatoxin B1 (AFB1) at 1-10-6 M concentration uncouples oxidative phosphorulation but does not affect the ADP:O ratio. At a concentration of 1-10-5 M, AFB1 also decreases the ADP:O ratio along with the uncoupling of oxidative phosphorylation. Aflatoxin G1 (AFG1) acts as an uncoupler at a relatively higher concentration of 1-10-4 M. Preincubation of mitochondria with these aflatoxins resulted in inhibition of respiration and uncoupling of rat liver mitochondria.
Insights
Aflatoxins M1, B1, and G1 inhibit mitochondrial electron transport. Aflatoxin M1 and B1 uncouple oxidative phosphorylation, impacting cellular energy production.
Area of Science:
- Biochemistry
- Toxicology
- Mitochondrial Function
Background:
- Aflatoxins are toxic metabolites produced by Aspergillus fungi.
- These toxins pose a significant risk to human and animal health.
- Understanding their impact on cellular respiration is crucial.
Purpose of the Study:
- To investigate the in vitro effects of aflatoxins M1, B1, and G1 on rat liver mitochondrial oxidative phosphorylation.
- To determine the specific site of inhibition within the electron transport chain.
- To characterize the uncoupling effects of these aflatoxins on cellular energy production.
Main Methods:
- In vitro study using isolated rat liver mitochondria.
- Succinate was used as the substrate for oxidative phosphorylation.
- Assays were performed to measure electron transport chain inhibition and ADP:O ratios.
Main Results:
- All tested aflatoxins (M1, B1, G1) inhibited the electron transport chain at 1-10⁻⁴ M, with inhibition occurring between cytochrome b and cytochrome c/c1.
- Aflatoxin M1 uncoupled oxidative phosphorylation at 1-10⁻⁶ M, reducing the ADP:O ratio.
- Aflatoxin B1 uncoupled phosphorylation at 1-10⁻⁶ M without affecting the ADP:O ratio, but decreased it at 1-10⁻⁵ M.
- Aflatoxin G1 acted as an uncoupler at a higher concentration (1-10⁻⁴ M).
- Preincubation with aflatoxins inhibited mitochondrial respiration and caused uncoupling.
Conclusions:
- Aflatoxins M1, B1, and G1 interfere with mitochondrial energy production by inhibiting the electron transport chain and uncoupling oxidative phosphorylation.
- The specific mechanisms and effective concentrations vary among the different aflatoxins.
- These findings highlight the mitochondrial toxicity of aflatoxins, contributing to their overall toxicological profile.