Metabolism of Elements in Mammals and Vertebrates
A remarkable feature of iron metabolism is that there is no specific excretory mechanism for iron, or if there is one (as yet to be discovered), the excretion rate is very low. Iron will, however, be lost through hemorrhage and other incidents. Organisms use iron very economically. It is essential and required in substantial quantity, but rather hard to obtain. Thus, organisms cannot afford to lose it easily and hence have developed extensive mechanisms to utilize their iron over and over again. Two-thirds of all the iron in mammals is in the form of hemoglobin. The daily iron turnover caused by destruction of red blood cells is equivalent to about 2% of that in all the hemoglobin. However, this iron is reutilized to produce more hemoglobin. The average half-life of hemoglobin iron has been estimated to be about 8 years in an adult human (Finch and Loden, 1959). This is enormously long, compared to, for example, the half-life of calcium in bone, which is also considered to be “long” but estimated to be less than 9 months.
KeywordsCholesterol Nickel Fermentation Chromium Dopamine
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