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Notes:
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Objective: to examine the effect of fecal absence on experimental
colon carcinogenesis in both male and female rats.
Material and methods: a total of 138 10-week-old Sprague-
Dawley, male and female rats were divided into five groups: A) 20
rats, no treatment; B) 26 rats, colonic defunctionalization; C) 30
rats, 18 weekly doses of dimethylhydrazine (DMH), 21 mg/kg
body weight each, from the beginning of the study; D) 20 rats,
ethylen-diamine-tetraacetic acid for 18 weeks; and E) 42 rats,
same surgical procedure as rats in group B plus DMH injections at
the same doses as rats in group C. Animals were sacrificed after
25-27 weeks. Number of tumors, their location, and pathological
findings were all compared between groups.
Results: no tumors developed in the dimethylhydrazine-free
groups. No differences were obtained either in number of tumors
or tumors per rat for group C as compared to group E. Fecal absence
was associated with smaller-sized tumors (p = 0.007),
greater numbers of non-mucinous tumors (p = 0.00009), better
differentiation (p = 0.0054), and lesser penetration into the wall
(p = 0.015) for group E as compared to group C. In the dimethylhydrazine
group, fecal absence altered the number of tumors developing
in males as compared to female rats (p = 0.025). Moreover,
this fecal absence showed no inhibitory effect on right
colonic tumors (p = 0.0065).
Conclusions: fecal absence alters the DMH-carcinogenic pattern
in the defunctionalized colon when using an experimental
model in both male and female rats. |
