Factors influencing the absorption of iron and copper from the alimentary tract.

ALTHOUGH the importance of Fe in respiratory processes has been recognized for a long period, there are still gaps in our knowledge of the many processes in which this element is involved, e.g. very little is known concerning the absorption of Fe from the alimentary tract. The work to be described is concerned with this problem. The Wisconsin workers [Hart et al. 1928; Elvehjem, 1932] have produced evidence to show that "inorganic" Fe but not haematin Fe can be absorbed from the alimentary tract and subsequently converted into haemoglobin. There has been much controversy as to whether both ferrous and ferric Fe or only the ferrous form can be absorbed as such. Heubner [1926] and Lintzel [1931] state that ferric but not ferrous Fe forms non-dialysable compounds with proteins and they believe that ferric Fe cannot be absorbed as such but must first be reduced to the ferrous state. They consider the intestine to be the site of this reduction as it contains easily oxidizable materials and has a low oxygen tension. This view is supported by Starkenstein & Weden [1930], Reimann & Fritsch [1930] and Moore et al. [1939]. Other workers believe that ferric Fe can be absorbed as such [Whipple & Robscheit-Robbins, 1936; McCance & Widdowson, 1937; 1938; Brock & Hunter, 1937]. These workers base their views on the following considerations: (1) in balance experiments, ferric Fe has been found to be absorbed as easily as ferrous Fe; (2) in the treatment of anaemia, ferric Fe often produces as good a response as ferrous Fe. Those who hold the first view have in no case produced any evidence that reduction of ferric Fe does take place in any part of the alimentary tract. Tompsett [1934, 2] has shown that whereas ferric Fe could be recovered quantitatively in trichloroacetic acid extracts of materials containing simple proteins, it could not be recovered from materials containing phosphatides and phosphoproteins. Extraction of ferrous Fe was not so affected. It seems that the absorption of Fe from the alimentary tract is more likely to be hindered by phosphoproteins and phosphatides than by simple proteins. In previous communications Tompsett [1939, 2, 3] has shown that the absorption of lead is highest on a low calcium diet and least on a high calcium diet and is increased by the addition of mineral acid to the diet. In all probability, Fe absorption is influenced by similar factors.