Iron absorption and biliary excretion of transferrin in rats

The content of transferrin, albumin, and iron was determined in plasma and bile from normal and iron-deficient rats. In the plasma as well as in the bile there is a decrease of iron and an increase of transferrin due to iron depletion, whereas the albumin level remains constant. No significant difference of iron contents in plasma and bile was found, but the content of transferrin and albumin in bile was markedly lower than in the plasma. Thus, in the bile the iron content substantially exceeded the binding capacity of transferrin. The ratio between transferrin and albumin was the same in bile as in blood which argues for a bulk transfer of plasma proteins into the bile.