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Effect of aflatoxin B in vitro on rat liver mitochondrial respiratory functions
M P Sajan1, J G Satav, R K Bhattacharya
1Radiation Biology and Biochemistry Division, Bhabha Atomic Research Centre, Bombay, India.
Abstract:
Isolated rat liver mitochondria were incubated with various concentrations of aflatoxin B (AFB) for different periods of time. Respiration rates were then measured with two substrates (succinate and glutamate). State 3 respiration rate (with added ADP) declined with increase in preincubation concentrations of AFB1 (0.15-0.50 mM). On the other hand, state 4 respiration rate (after depletion of added ADP) was found to increase with increased pretreatment concentration of AFB. As a consequence, respiratory control index was reduced attaining minimum value with 0.25 mM AFB and preincubation time of 10 min. The induced anomaly in mitochondrial respiratory functions appear to be due to membrane damage caused by interaction of reactive AFB1 metabolite generated by mitochondrial cytochrome P-450 enzymes with mitochondrial components.
Insights
Aflatoxin B (AFB) disrupts rat liver mitochondrial respiration, decreasing state 3 and increasing state 4 rates. This leads to reduced respiratory control, suggesting AFB-induced membrane damage.
Area of Science:
- Biochemistry
- Toxicology
- Mitochondrial Physiology
Background:
- Aflatoxin B1 (AFB) is a toxic metabolite produced by Aspergillus fungi.
- AFB is a known hepatotoxin and carcinogen.
- Mitochondria are crucial for cellular energy production and are targets of toxic compounds.
Purpose of the Study:
- To investigate the effects of aflatoxin B1 (AFB) on isolated rat liver mitochondrial respiratory function.
- To determine the concentration and time-dependent effects of AFB on mitochondrial respiration.
- To elucidate the mechanism underlying AFB-induced mitochondrial dysfunction.
Main Methods:
- Isolated rat liver mitochondria were preincubated with varying concentrations of AFB (0.15-0.50 mM) for different durations.
- Mitochondrial respiration rates were measured using succinate and glutamate as substrates.
- State 3 (ADP-stimulated) and State 4 (non-phosphorylating) respiration rates were assessed.
- Respiratory control index (RCI) was calculated.
Main Results:
- State 3 respiration rate significantly declined with increasing AFB concentrations.
- State 4 respiration rate increased with higher AFB pretreatment concentrations.
- Respiratory control index (RCI) was reduced, reaching a minimum at 0.25 mM AFB and 10 min preincubation.
- These changes suggest AFB-induced damage to the mitochondrial membrane.
Conclusions:
- Aflatoxin B1 impairs mitochondrial respiratory function in a concentration-dependent manner.
- The observed effects are likely due to AFB-induced mitochondrial membrane damage.
- Reactive AFB1 metabolites generated by mitochondrial cytochrome P-450 enzymes contribute to mitochondrial dysfunction.