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Postmortem oxygen consumption by mitochondria and its effects on myoglobin form and stability
Jiali Tang1, Cameron Faustman, Thomas A Hoagland
1Department of Animal Science, University of Connecticut, 3636 Horsebarn Hill Road Ext., Storrs, Connecticut 06269-4040, USA.
Abstract:
The objective of this study was to assess the morphological integrity and functional potential of mitochondria from postmortem bovine cardiac muscle and evaluate mitochondrial interactions with myoglobin (Mb) in vitro. Electron microscopy revealed that mitochondria maintained structural integrity at 2 h postmortem; prolonged storage resulted in swelling and breakage. At 2 h, 96 h, and 60 days postmortem, the mitochondrial state III oxygen consumption rate (OCR) and respiratory control ratio decreased with time at pH 7.2 and 5.6 (p < 0.05). Mitochondria isolated at 60 days did not exhibit ADP-induced transitions from state IV to state III oxygen consumption. Tissue oxygen consumption also decreased with time postmortem (p < 0.05). Mitochondrial oxygen consumption was inhibited by decreased pH in vitro (p < 0.05). In a closed system, mitochondrial respiration resulted in decreased oxygen partial pressure (pO(2)) and enhanced conversion of oxymyoglobin (OxyMb) to deoxymyoglobin (DeoMb) or metmyoglobin (MetMb). Greater mitochondrial densities caused rapid decreases in pO(2) and favored DeoMb formation at pH 7.2 in closed systems (p < 0.05); there was no effect on MetMb formation (p > 0.05). MetMb formation was inversely proportional to mitochondrial density at pH 5.6 in closed systems. Mitochondrial respiration in open systems resulted in greater MetMb and DeoMb formation at pH 5.6 and pH 7.2, respectively, vs controls (p < 0.05). The greatest MetMb formation was observed with a mitochondrial density of 0.5 mg/mL at both pH values in open systems. Mitochondrial respiration facilitated a shift in Mb form from OxyMb to DeoMb or MetMb, and this was dependent on pH, oxygen availability, and mitochondrial density.
Insights
Postmortem bovine cardiac mitochondria lose structural and functional integrity over time. Mitochondrial respiration alters myoglobin forms, influenced by pH, oxygen, and density.
Area of Science:
- Mitochondrial biology
- Biochemistry
- Postmortem tissue analysis
Background:
- Mitochondria are crucial for cellular energy production.
- Myoglobin (Mb) plays a role in oxygen transport and storage in muscle.
- Understanding postmortem changes in cardiac mitochondria is vital for tissue preservation and research.
Purpose of the Study:
- To assess the morphological and functional integrity of postmortem bovine cardiac mitochondria.
- To evaluate the in vitro interaction between mitochondria and myoglobin.
Main Methods:
- Electron microscopy for morphological assessment.
- Measurement of mitochondrial oxygen consumption rate (OCR) and respiratory control ratio.
- In vitro incubation of mitochondria with myoglobin under varying pH and oxygen conditions.
Main Results:
- Mitochondria maintained integrity up to 2 hours postmortem, with degradation thereafter.
- Mitochondrial function (OCR, RCR) declined significantly with prolonged storage and lower pH.
- Mitochondrial respiration altered myoglobin forms (OxyMb to DeoMb/MetMb), dependent on pH, oxygen, and mitochondrial density.
Conclusions:
- Postmortem bovine cardiac mitochondria exhibit progressive structural and functional decline.
- Mitochondrial respiration directly influences myoglobin redox state and form.
- These findings have implications for understanding postmortem muscle biochemistry and potential applications in tissue research.
