Myoglobin

Myoglobin is the oxygen-binding protein of the skeletal muscles and the heart. The molecular weight is 17.8 kD. Myoglobin originates exclusively from the cytoplasm of striated but not smooth muscle cells. It permeates rapidly into the extracellular space when the cells are damaged. The plasma half-life after release from the muscles is about 15 minutes; elimination takes place by glomerular filtration via the kidneys. In renal insufficiency, myoglobin accumulates in the blood; positive myoglobin values can therefore be misinterpreted.

Myoglobin shows structural and functional homology to haemoglobin. However, in contrast to haemoglobin, it consists of only 1 peptide chain with 153 amino acids. Furthermore, myoglobin contains one iron-bearing heme group per molecule. Myoglobin acts as an oxygen storage of the muscle tissue, through which oxygen can be quickly mobilised for biological oxidation (respiratory chain) when the muscle is working.

Standard value: The reference range for women is between 25 and 58 µg/l, for men between 28 and 72 µg/l

The most common causes of an increase of myoglobin in the blood are:

Heart attack in the early stages: maximum around 4-6 hours, normalization after about (12-) 24 hours. GOT and LDH are also released from the myocardial cells with myoglobin, but they have longer half-lives.

Other causes of rhabdomyolysis.

During evolution, haemoglobins branched off from the phylogenetically older myoglobin about 600 million years ago.