In:
British Journal of Haematology, Wiley, Vol. 40, No. 3 ( 1978-11), p. 401-414
Abstract:
S ummary . The in vivo incubation of intrinsic factor‐[ 57 Co]vitamin B 12 in an ileal loop of a guinea‐pig followed of in vitro culturing of segments of the ileum for 180 min has been used to study the transepithelial transport vitamin B 12 . Analysis of the solubilized supernate of mucosa following the in vivo phase demonstrated that 44% of the [ 57 Co]vitamin B 12 was bound to intrinsic factor (IF), 26% was free, and 16% was bound to transcobalamin II (TCII). Following culture, similar analysis demonstrated that 18% of the vitamin was now bound to IF, 49% was free, and 35% was bound to TCII. In the culture medium, 54% of the [ 57 Co]vitamin B 12 was free and 37% was bound ot TCII. The formation of TCII‐[ 57 ]vitamin B 12 did not occur if homogenized mucosa was incubated with free [ 57 Co]vitamin B 12 but it did form in cultures of ileal segments from animals given an excess of unlabelled vitamin to saturate all circulating TCII, and in the medium containing puromycin. Indirect immunoflourescence using chicken anti‐TCII demonstrated that TCII was associated with the mucosal cells of both the ileum and jejunum. These studies demonstrate that following transepithelial flux of vitamin B 12 through the ileal mucosa, the vitamin becomes coupled to TCII. This coupling requires a structurally intact mucosa and the source of the TCII appears to be the ileal mucosal cell rather than unsaturated TCII circulating in the blood.
Type of Medium:
Online Resource
ISSN:
0007-1048
,
1365-2141
DOI:
10.1111/bjh.1978.40.issue-3
DOI:
10.1111/j.1365-2141.1978.tb05812.x
Language:
English
Publisher:
Wiley
Publication Date:
1978
detail.hit.zdb_id:
1475751-5
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