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-Irradiation in the Colorectum of Rats Treated with an Immunosuppressant1
Laboratory of Nutritional Biochemistry, Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
2To whom correspondence should be addressed.
We demonstrated recently that
-irradiation can induce aberrant
crypt foci (ACF) in the rat colorectum. The aim of this study was to
evaluate the effect of dietary sugar beet fiber (SBF) on the
distribution of the CD8+ intraepithelial lymphocyte (IEL)
in the colorectum and on the number of
-irradiationinduced ACF of
rats administered anti-asialo GM1 (
AGM1) as an
immunosuppressant. Wistar/ST rats fed a fiber-free diet or the diet
supplemented with SBF (100 g/kg diet) were administrated
AGM1 or
normal rabbit serum as a control during the initiation period with
-irradiation. At 5 and 9 wk after the first irradiation, ACF and
total aberrant crypts (AC) per area in the colorectum were counted. The
numbers of ACF (P = 0.0010) and AC
(P = 0.0635) per unit area were lower in the
SBF-fed group than in the rats fed the fiber-free diet.
AGM1
administration significantly raised the number of ACF (P
= 0.0001) and AC (P = 0.0006) per area in the
colorectum. Moreover,
AGM1 administration during the initiation
period reduced the number of CD8+ IEL per 100 cells in the
epithelial layer (P = 0.0001) of the colon. These
results demonstrate that reduction of the number of CD8+
IEL per 100 cells in the epithelial layer as a result of
AGM1
administration promotes the formation of irradiation-induced ACF in
the colorectum. The number of CD8+ IEL per 100 cells in
epithelial layer was lower in the group fed the fiber-free diet
than in the SBF-fed group (P = 0.0522). These
results indicated that the ingestion of dietary SBF suppressed
-irradiationinduced ACF formation through the immune surveillance
in the colorectal mucosa.
KEY WORDS: aberrant crypt foci anti-asialo GM1 CD8+ intraepithelial lymphocyte rats sugar beet fiber
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