Læknablaðið : fylgirit - 01.05.1978, Blaðsíða 148

Table I. BACTERIAL UPTAKE O? FREE AND LBP-BOUND BJ2
Bacteria No. of experiments B12 Free B 12 aptake LBP-bound B^
E. coli 5 + -
Proteus mirabilis 5 + -
Pseudomonas species 3 + -
Pseudomonas aeruginosa 1 + -
Aeromonas species 2 + -
Klebsiella peum. 4 + -
Enterococci 2 -
of vitamin B12. However, intrinsic-factor-
bound B12 is only partly protected from being
taken up by coli, coliforms and bacteroides
(3,15). This could explain the B12 malabsorption
often accompanying conditions with overgrowth of
a faecal type of flora in the small intestine.
We are studying how LBP affects the uptake of
B12 by intestinal bacteria. For this purpose we
have used LBP purified from extracts of porcine
gastric mucosa by affinity chromatography mainly
according to Allen et al. (1).
Bacteria cultured for about 16 h. in a Bi^-free
medium were incubated aerobically for up to 3 h.
at 37°C in 0.6 ml portions containing 70 fmol of
either free or LBP-bound57co-cyanocobalamin
(spec. act. 200 mCi/nig) per 106 - 108 cells.
After centrifugation of the incubated mixtures
the sediments were washed twiee with saline.
The amount of B12 taken up by the bacteria was
measured by counting the radioactivity of the
sediment.
In order to investigate, whether or not LBP
or EDTA could remove already bacteria-bound
B12, experiments were performed with LBP and
EDTA (final concentration 0.25 or 0.005 M),
respectively, added either within 1 min. or 1 h.
after the addition of the B12. The bacteria
were incubated with the LBP or EDTA for 15
min. before centrifugation.
Fig. 1 shows the result of an experiment
with Escherichia coli. LBP inhibited the
uptake of B12 by the bacteria incubated for up
to 3 h.
Table I demonstrates that LBP invariably
inhibited the uptake of B12 all B12- uptaking
bacteria that we have studied.
Fig. 2 demonstrates experiments with LBP
and EDTA added after the B12 to different
MINITKS
Fig. 2 Incubation experiments with LBP and
EDTA added within 1 min. or 1 hour
- after the addition of 57Co-cyanocobala-
min to bacteria suspensions. The
triangles represent LBP, the filled
circles 0.25 M EDTA, the unfilled
circles 0.005 M EDTA, and the squares
Hank's solution.
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