Is haemosiderin always haemoglobin derived?

[scilearner]

Hello everyone,

Haemosiderin definition says that it is a pigment that occurs when there is a local or systemic excess of iron. Does that mean excess iron deposition can cause haemosiderin pigment, I mean you don't alway need macrophages to eat Hb and make it, just iron is enough. Thanks

 

[CharonY]

I am not quite sure what the question is, but hemosiderin occurrence is linked to ferritin, in fact it appears a metabolized form of ferritin. As such it is a means to reduce intracellular free iron. The source of the iron does not play a major role in this regard, i.e. neither the ferritin molecules nor the responsible regulators do not know where the rise in iron content comes from.

The reason why it is being linked to Hb degradation in certain textbooks is that hemosiderins are often found in macrophages and in these cases a plausible source is the degradation of red blood cells. However, it is only one example to describe the situation where hemosiderin may be observed and is not the biochemical pathway leading to its formation per se (nor its biological role, for that matter).