1) Whole body counting by means of a large phosphor well scintillation counter has been used to measure the absorption of Fe59-tagged inorganic iron, and shown to compare favourably with other methods.
2) There is a delay in the fecal elimination of the unabsorbed portion of the dose of Fe59 by iron-deficient rats on iron-deficient diet. The cause of this delay is unknown but it may be associated with the marked cecal enlargement which exists in these animals.
3) It is confirmed that iron deficiency is associated with striking enhancement of absorption of ferrous and ferric inorganic iron.
4) When a series of doses of ferrous iron of increasing size from 5 to 1,000 µg. was given, there was a progressive increase in absorption for each increase in dose in both iron-supplemented and iron-deficient rats. The relationship between amount of iron given and amount absorbed suggests that two processes may be involved: 1) simple diffusion, and 2) a carrier mechanism.
5) The effect on iron absorption of a sudden change in iron intake has been investigated. Switch from a low to high iron diet reduces absorption, and from a high to a low iron diet increases absorption, too rapidily for hemoglobin level or body iron stores alone to be the most important governing factors and this finding emphasizes the importance of local changes in the intestine.