Iron is a necessary constituent of red blood cells, so its radioactive
form, ⁵⁹Fe, has been used frequently in measurement of the rate of
formation of red cells, the lifetime of red cells, and red cell volumes.
The labeling is more difficult than labeling with chromium for the same
purposes, so this procedure no longer has the importance it once had.
On the other hand, direct measurement of absorption of iron by the
digestive tract can be accomplished only by using ⁵⁹Fe. In
_achlorhydria_ the gastric juice in the stomach is deficient in
hydrochloric acid, and this condition has been shown to lower the iron
absorption. A normal diet contains much more iron than the body needs,
but in special cases, sometimes called “tired blood” in advertising for
medicines, iron compounds are prescribed for the patient. If ⁵⁹Fe is
included, its appearance in the blood stream can be monitored and the
effectiveness of the medication noted.
[Illustration: _This multiple-port scintillation counter is used for
iron-kinetic studies. The tracer dose of iron-59 is administered into
the arm vein and then the activities in the bone marrow, liver, and
spleen are recorded simultaneously with counters positioned over these
areas, and show distribution of iron-59 as a function of time. When the
data are analyzed in conjunction with iron-59 content in blood,
information can be obtained about sites of red blood cell production and
destruction._]