Blood, 1957, Vol. 12, No. 4, pp. 336-346.
© 1957 American Society of Hematology, Inc.
Radioactive Vitamin B12 Absorption Studies: Results of
Direct Measurement of Radioactivity in the Blood
ALFRED DOSCHERHOLMEN 1,
PAUL S. HAGEN 1, and
MARGARET LIU 1
1 Hematology Section, Medical Service, Veterans Administration Hospital,
Minneapolis, Minnesota, and the Department of Medicine, University of Minnesota Medical
School.
A new method for the determination of the absorption of vitamin B12 has been
described using measurement of radioactivity in the blood or plasma after the
ingestion of physiologic test doses of Co60 labeled vitamin B12.
Although doses of 1.0 µc. (0.92 µg. vitamin B12) gave higher counts, equally
reliable results were obtained with 0.5 µc. (0.46 µg. vitamin B12). The radioactivity
was found in the plasma portion of the blood.
With this method it was possible to differentiate between all of nine patients
with pernicious anemia and 36 control subjects.
In non-pernicious anemia subjects and in pernicious anemia patients given
intrinsic factor, there was a relatively delayed rise in the blood or plasma radioactivity until a peak was reached in the 8 to 12 hour interval after the ingestion
of the test dose. This absorption curve was quite different from the early rise observed by others after massive oral doses of vitamin B12, indicating a different
mode of absorption.
Following the peak blood concentration the radioactivity gradually declined
and small amounts usually persisted for as long as one week, quite different from
the rapid disappearance after parenteral administration previously reported.
This method appears valuable in the diagnosis of pernicious anemia and other
vitamin B12 malabsorptive states, in the evaluation of intrinsic factor activity,
and in studies of various aspects of the metabolism of vitamin B12.
Submitted on June 25, 1956
Accepted on August 12, 1956
