Manganese metabolism is impaired in the Belgrade laboratory rat

Homozygous Belgrade rats have a hypochromic anaemia due to impaired iron transport across the cell membrane of immature erythroid cells. This study aimed at investigating whether there are also abnormalities of Mn metabolism in erythroid and other types of cells, The experiments were performed with homozygous (bib) and heterozygous (+/b) Belgrade rats and Wistar rats and included measurements of Mn uptake by reticulocytes in vitro, Mn absorption from in situ closed loops of the duodenum, and plasma clearance and uptake by several organs after intravenous injection of radioactive Mn bound to transferrin (Tf) or mixed with serum. Similar measurements were made with Fe-59-labelled Fe in several of the experiments, Mn uptake by reticulocytes and absorption from the duodenum was impaired in bb rats compared with +/b or Wistar rats. The plasma clearance of Mn-Tf was much slower than Mn-serum, but both were faster than the clearance of Fe-Tf. Uptake of Mn-54 by the kidneys, brain and femurs was less in b/b than Wistar or +/b rats, but uptake by the liver was greater in bib rats. Similar differences were found for Fe-59 uptake by kidneys, brain and femurs but Fe-59 uptake by the liver was also impaired in the liver. II is concluded that the genetic abnormality present in b/b rats affects Mn metabolism as well as Fe metabolism and that Mn and Fe share similar transport mechanisms in the cells of erythroid tissue, duodenal mucosa. kidney and blood-brain barrier.