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Enhancement by thyroxine of experimental carcinogenesis induced in rat colon by azoxymethane
Author(s) -
Iishi Hiroyasu,
Tatsuta Masaharu,
Baba Miyako,
Okuda Shigeru,
Taniguchi Haruo
Publication year - 1992
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.2910500625
Subject(s) - azoxymethane , medicine , histology , carcinogen , gastroenterology , distal colon , pathology , incidence (geometry) , colorectal cancer , endocrinology , biology , cancer , physics , optics , genetics
The effect of thyroxine (T 4 ) on the incidence, number and histology of colon tumors induced by azoxymethane (AOM), and on the labeling index of colon mucosa were investigated in Wistar rats. Rats were given AOM by injection once a week for 10 weeks, together with T 4 in depot form until the end of the experiment. Administration of T 4 resulted in a significant increase in the incidence of colon tumors in week 35. However, it did not influence the histological appearance of the colon tumors or the histological types and depths of involvement of colon adenocarcinomas. Furthermore, it caused a significant increase in the labeling index of the colon during, but not after, AOM treatment. Our findings indicate that T 4 enhances the development of colon tumors, which may be related to its effect in increasing proliferation of epithelial cells in the colon mucosa during administration of the carcinogen.