Myoglobin turnover

Most of the iron in the body is in the form of haemoglobin in red blood cells and myoglobin in muscle. The remainder is in the liver, spleen and other tissues. Haemoglobin is essential for the proper functioning of every organ and tissue of the body. Iron has a rapid turnover rate in the chicken therefore, it must be provided in a highly available form in the diet on a daily basis. Iron deficiency can result in microcytic, hypochromic anaemia in poultry. Any internal infection such as coccidiosis can also interfere with iron absorption and lead to a deficiency. 

In adults some 250-400 mg of bihmbin is produced daily 70-80% is derived from degradation of the haem moiety of haemoglobin, 20-25% is derived from the hepatic turnover of haem proteins, such as myoglobin, cytochromes and catalase. 

Elevations in cTnl and cTnT are highly specific for myocardial injury. However, in individuals without myocardial disease, their levels are very low to undetectable. This is in contrast to the low but measurable concentrations of CK-2 and myoglobin detected in serum from skeletal muscle turnover in patients with noncardiac-related diseases and in normal individuals. Therefore release of cTnl or cTnT from myocardium into the blood following AMI and after the washout that accompanies successful reperfusion generates an excellent signal compared with no detectable baseline levels before myocardial damage. The initial rapid release of cardiac troponin subunits I and T following successful reperfusion is most hkely derived from the soluble cytosolic myocardial fraction (6% cTnT 3% cTnl). 

In liver, muscle and other tissues iron is taken up by the cells when transferrin saturation levels are high and deposited first in ferritin and subsequently transferred to haemosiderin. This pool of ferritin iron is most likely used within these cells to meet requirements for synthesis of haem enzymes, myoglobin and other non-haem iron proteins. The ferritin can also store iron released from the breakdown of such iron containing proteins in the course of their turnover. Mobilisation of iron from these tissues once again probably involves reduction of iron to Fe2+ and its transfer across the cell membrane to transferrin. In such tissues the level of transferrin saturation seems likely to play a major role in determining the balance between deposition of iron in ferritin and its mobilization from the storage form. 

The turnover time of intact Lb is relatively short [reviewed in (37)], cf. the long half-lives of myoglobin and hemoglobin in mammals, with the major Lb components of pea nodules having turnover times of about two days (49). This is considerably less than the lifetime of the nitrogenase (50). There must therefore be continual synthesis and degradation of Lb within the host cell cytoplasm, and there is evidence for dramatic changes (as mentioned earlier) in relative concen-... 

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