Determine the fate of manganese which is absorbed?
Let us now study the fate of Mn which is absorbed.
After absorption, Mn is complexed with albumin and transported to the liver, which is the key organ in its metabolism. In the liver, Mn is found in both rapid and slow exchanging pools. The former is the precursor of biliary Mn, which is excreted in the faeces. The latter serves as the source of Mn for the liver and extra hepatic tissues. Mn becomes bound as Mn2 + to a-macroglobulin before traversing the liver. From the liver, some Mn2+ appears to be oxidized by ceruloplasmin to Mn3+ and complexes with transfenin. Transferrin bound Mn3+ is taken up by the extrahepatic tissues. Mn is found in most organs and tissues and preferentially accumulates in the mitochondria. There is no storage form for Mn. Bone contains substantial amount of mineral but there is no mechanism to release it and thus bone Mn is considered as passive storage. It is released only as a result of normal bone turnover or in situations of accelerating bone resorption. Mn is almost totally excreted in the faeces (92%). Excess absorbed MI is quickly excreted by the liver into the bile to maintain homeostasis. Only trace amounts are excreted in urine.