Summary
This protocol describes a procedure to study the respiration of mitochondria isolated from skeletal muscles. This method was adapted from Scorrano et al. (2007). The mitochondrial isolation procedure requires about 2 hours. The mitochondrial respiration can be completed in about 1 hour.
Abstract
Mitochondria are organelles controlling the life and death of the cell. They participate in key metabolic reactions, synthesize most of the ATP, and regulate a number of signaling cascades2,3. Past and current researchers have isolated mitochondria from rat and mice tissues such as liver, brain and heart4,5. In recent years, many researchers have focused on studying mitochondrial function from skeletal muscles.
Here, we describe a method that we have used successfully for the isolation of mitochondria from skeletal muscles 6. Our procedure requires that all buffers and reagents are made fresh and need about 250-500 mg of skeletal muscle. We studied mitochondria isolated from rat and mouse gastrocnemius and diaphragm, and rat extraocular muscles. Mitochondrial protein concentration is measured with the Bradford assay. It is important that mitochondrial samples be kept ice-cold during preparation and that functional studies be performed within a relatively short time (~1 hr). Mitochondrial respiration is measured using polarography with a Clark-type electrode (Oxygraph system) at 37°C7. Calibration of the oxygen electrode is a key step in this protocol and it must be performed daily. Isolated mitochondria (150 μg) are added to 0.5 ml of experimental buffer (EB). State 2 respiration starts with addition of glutamate (5mM) and malate (2.5 mM). Then, adenosine diphosphate (ADP) (150 μM) is added to start state 3. Oligomycin (1 μM), an ATPase synthase blocker, is used to estimate state 4. Lastly, carbonyl cyanide p-[trifluoromethoxy]-phenyl-hydrazone (FCCP, 0.2 μM) is added to measurestate 5, or uncoupled respiration 6. The respiratory control ratio (RCR), the ratio of state 3 to state 4, is calculated after each experiment. An RCR ≥4 is considered as evidence of a viable mitochondria preparation.
In summary, we present a method for the isolation of viable mitochondria from skeletal muscles that can be used in biochemical (e.g., enzyme activity, immunodetection, proteomics) and functional studies (mitochondrial respiration).
Protocol
Discussion
We present a protocol to isolate viable mitochondria from skeletal muscles. If yield is a problem, the protocol can be modified by incubating the isolated muscle in 5 ml of PBS/10mM EDTA/0.01% trypsin for 30 minutes in ice. To assure complete muscle digestion with trypsin, the muscle needs to be fully minced. After the 30-minute incubation, the PBS/10mM EDTA/0.01% trypsin solution must be completely replaced with 3 ml of isolation buffer 1 (IB1). In addition, the use of trypsin may interfere with some mitochondrial subst…
Declarações
The authors have nothing to disclose.
Acknowledgements
This work was supported by a grant from the National Eye Institute (R01 EY12998) to F.H. Andrade.
Materials
| Material Name | Tipo | Company | Catalogue Number | Comment |
|---|---|---|---|---|
| 95% CO2 / 5% O2 mix | Local gas company | |||
| Adenosine 5′-diphosphate sodium salt | Sigma | A2754 | ||
| Blue Rizla Paper | Hansatech | 890101 | ||
| Bradford protein assay | Bio-Rad | 500-0006 | ||
| Carbonylcyanide p-trifluoromethoxyphenylhydrazone (FCCP) | Sigma | C2920 | ||
| Centrifuge 5804R | Eppendorf | |||
| Compressed nitrogen | Local gas company | |||
| D-mannitol | Sigma | M9647 | ||
| Ethlyene-glycol-bis-tetraacetic acid (EGTA) | Sigma | E3889 | ||
| Ethylenediaminetetraacetic acid (EDTA) | Bio-Rad | 161-0728 | ||
| Free fatty acid bovine serum albumin | Sigma | A8806 | ||
| Glutamic acid | Sigma | G5889 | ||
| HEPES sodium salt | Sigma | H7006 | ||
| Isotemp 3006D | Fisher Scientific | |||
| Magnesium chloride | Sigma | M8266 | ||
| Male Sprague Dawley Rats | Harlan | 300-500g | ||
| Malic acid | Sigma | M9138 | ||
| Minifuge | ISC Bioexpress | C1301P | ||
| Oligomycin | Sigma | O4876 | ||
| Oxygen electrode disc | Hansatech | S1 | ||
| Oxygraph | Hansatech | |||
| Oxygraph Plus V1.01 Software | Hansatech | |||
| pH-meter | Mettler Toledo | 1225506149 | ||
| Phosphate-buffered saline (PBS) | Sigma | P4417 | ||
| Potassium chloride | Sigma | P3911 | ||
| Potassium phosphate | Sigma | P8416 | ||
| Potter-Elvehjem homogenizers | Fisher | 08-414-14A | ||
| PTFE (0.0125mm × 25mm) membrane | Hansatech | S4 | ||
| SKIL 3320 drill press | Hardware store | |||
| Sucrose | Sigma | S5016 |
Referências
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- Gamboa, J. L., Andrade, F. H. Mitochondrial content and distribution changes specific to mouse diaphragm after chronic normobaric hypoxia. Am J Physiol Regul Integr Comp Physiol. , (2009).
- Patel, S. P., Gamboa, J. L., McMullen, C. A., Rabchevsky, A., Andrade, F. H. Lower respiratory capacity in extraocular muscle mitochondria: evidence for intrinsic differences in mitochondrial composition and function. Invest Ophthalmol Vis Sci. 50, 180-186 (2009).
- Bradford, M. M. A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Anal Biochem. 72, 248-254 (1976).
