Effect of defunctionalization on colon carcinogenesis in the rat.
OBJECTIVE
to examine the effect of fecal absence on experimental colon carcinogenesis in both male and female rats.


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.
Pérez-Holanda
S
S
Department of Surgery. Hospital Valle del Nalón. Langero, Asturias. Spain. sergio.perez-holanda@sespa.princast.es
Rodrigo
L
L
Viñas-Salas
J
J
Piñol-Felis
C
C
Ildefonso
C
C
D000818:Animals; D015179:Colorectal Neoplasms / Q000209:etiology / Q000473:pathology; D004127:Dimethylhydrazines / Q000008:administration & dosage; D005243:Feces; D005260:Female; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley
D004127:Dimethylhydrazines