Myoglobin

myoglobin

Muscle tissues

Myoglobin (MB) is a protein found in muscles.

Description
Myoglobin is an iron-containing cytoplasmic hemoprotein, expressed solely in cardiac myocytes and skeletal/ striated muscle fibers. The MB gene encodes myoglobin roduction. This protein has several forms such as oxymyoglobin (MbO2), carboxymyoglobin (MbCO), and metmyoglobin (met-Mb) what makes it similar to hemoglobin. Myoglobin transports oxygen from red blood cells to the mitochondria of muscle cells, later the oxygen is used in cellular respiration process to produce energy.

 

Myoglobin functions as a storage for O2 in muscle, which releases oxygen in case of hypoxia or anoxia (It occurs when a person exercises. This provides an ability of the body to remain active longer).
Myoglobin comprises of hemes, pigments that imply the color of red meat. The color of the meat is to some extent determined by the degree of oxidation of the myoglobin.
When the muscles are damaged, myoglobin is released into the bloodstream and its level can be evaluated by a blood test. Myoglobin is later eliminated from the bloodstream by the kidneys. Although too high level of myoglobin is likely to damage the kidney itself.

Reference values
The normal range is 0 to 85 ng/mL.

Indications
The test is performed when a damage to muscle tissues – heart and skeletal muscles is suspected. However, the test is not specific for myocardial infarction and there are other markers that show the heart damage more precisely. Although if myoglobin does not increase within 12 hours after the chest pain occurs, an infarction is very unlikely.
The test is also performed in case of a severe muscle injury, such as trauma or when the muscle is damaged due to the disease.

Muscle injury/damage may be suspected when the following symptoms are preseny:

• Muscular pain;

• Dark-colored urine;

• Fever;

• Fatigue;

• Nausea, dizziness and vomiting;

• Abdominal pain.

Interpretation

The level of myoglobin in the blood starts increasing within 2-3 hours after the muscle injury/heart attack and within 8-12 hours the level appears to reach its highest. Within one day the level returns back to normal.Level of myoglobin may raise due to:

  • Heart attack (myocardial infarction);
  • Malignant hyperthermia (extremely rare);
  • Muscular dystrophy and other muscular diseases;
  • Breakdown of muscle tissue results in the release of muscle fibers contents into the blood (the condition is called rhabdomyolysis);
  • Skeletal muscle inflammation (myositis);
  • Skeletal muscle ischemia (oxygen deficiency);
  • Seizures;
  • Skeletal muscle trauma;
  • Shock;
  • Renal insufficiency.

The test

The blood sample of 5 ml is needed for the test. Myoglobin may also be measured with a urine test (1 ml of urine is required). Normally there are no myoglobin in the urine.

Related: Myoglobin test

Risks

The risks are very low and complications such as bleeding, infection or hematome appear rarely