Effect of 3,5,3'-triiodo-L-thyronine on the incidence and growth kinetics of spontaneous mammary tumors in C3H/HeN mice.
The present study compares the incidence and growth kinetics of spontaneous mammary tumors in 3,5,3'-triiodo-L-thyronine (T3)-treated (0.7 microgram/day, i.p.) C3H/HeN retired breeder mice with tumors occurring spontaneously in this strain (0.15 M NaCl, i.p.). T3 treatment markedly increased the rate of tumor incidence but had no effect on tumor growth rate as measured by tumor doubling time. A comparison of tumor labeling index and mitotic index between the two groups showed no difference. A histological comparison of the mammary glands in the two groups showed no significant difference in number of hyperplastic alveolar nodules. However, ductal-alveolar development was more pronounced in the 0.15 M NaCl-treated control group; consistent with this observation was the finding of lower levels of serum prolactin in the T3-treated groups. Since mammary tumorigenesis was increased in T3-treated mice in spite of lower levels of serum prolactin, a well-known promoter of spontaneous mammary tumors in mice, a direct role for T3 in the process of tumor formation is suggested.
D000818:Animals; D002455:Cell Division / Q000187:drug effects; D003043:Cocarcinogenesis; D005260:Female; D006965:Hyperplasia; D008325:Mammary Neoplasms, Experimental / Q000453:epidemiology / Q000473:pathology*; D051379:Mice; D014284:Triiodothyronine / Q000494:pharmacology*
D014284:Triiodothyronine