In:
Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 103, No. 15 ( 2006-04-11), p. 5694-5699
Abstract:
There is a need for an improved test of human ability to assimilate dietary vitamin B 12 . Assaying and understanding absorption and uptake of B 12 is important because defects can lead to hematological and neurological complications. Accelerator mass spectrometry is uniquely suited for assessing absorption and kinetics of carbon-14 ( 14 C)-labeled substances after oral ingestion because it is more sensitive than decay counting and can measure levels of 14 C in microliter volumes of biological samples with negligible exposure of subjects to radioactivity. The test we describe employs amounts of B 12 in the range of normal dietary intake. The B 12 used was quantitatively labeled with 14 C at one particular atom of the dimethylbenzimidazole (DMB) moiety by exploiting idiosyncrasies of Salmonella metabolism. To grow aerobically on ethanolamine, Salmonella enterica must be provided with either preformed B 12 or two of its precursors, cobinamide and DMB. When provided with 14 C-DMB specifically labeled in the C2 position, cells produced 14 C-B 12 of high specific activity (2.1 GBq/mmol, 58 mCi/mmol) (1 Ci = 37 GBq) and no detectable dilution of label from endogenous DMB synthesis. In a human kinetic study, a physiological dose (1.5 μg, 2.2 kBq/59 nCi) of purified 14 C-B 12 was administered and showed plasma appearance and clearance curves consistent with the predicted behavior of the pure vitamin. This method opens new avenues for study of B 12 assimilation.
Type of Medium:
Online Resource
ISSN:
0027-8424
,
1091-6490
DOI:
10.1073/pnas.0601251103
Language:
English
Publisher:
Proceedings of the National Academy of Sciences
Publication Date:
2006
detail.hit.zdb_id:
209104-5
detail.hit.zdb_id:
1461794-8
SSG:
11
SSG:
12
