Greater inhibitory effects for testosterone than castration in rat thyroid tumorigenesis initiated by N-bis(2-hydroxypropyl)nitrosamine.
The effects of testosterone and castration on thyroid tumorigenesis subsequent to initiation by N-bis(2-hydroxypropyl)nitrosamine (DHPN) were investigated in male Wistar rats. Following 2 weekly i.p. injections of DHPN at the dose of 210 mg/100 g body weight, testosterone was administered in the diet at concentrations of 0.15% or 0.03% for 28 weeks. Castration was performed on a separate group of animals 1 week after the final injection of DHPN. The incidence of thyroid adenomas and carcinomas were 69% (9/13) and 15% (2/13), respectively, in rats treated with DHPN alone, 0% (0/15) and 6% (1/15) in rats treated with DHPN and 0.15% testosterone, 13% (2/15) and 13% (2/15) in rats treated with DHPN and 0.03% testosterone and 33% (5/15) and 33% (5/15) in the castrated animals initiated by DHPN. The reduction in adenoma development associated with testosterone treatment was significant at both concentrations. In contrast, only a tendency for decrease of thyroid tumor incidence was observed in rats castrated.
Kitahori
Y
Y
Second Department of Pathology, Nara Medical University, Japan.
Ohshima
M
M
Nakaoka
S
S
Fukumoto
M
M
Hiasa
Y
Y
D000818:Animals; D001835:Body Weight / Q000187:drug effects; D008297:Male; D009602:Nitrosamines; D009919:Orchiectomy; D009929:Organ Size / Q000187:drug effects; D011467:Prostate / Q000033:anatomy & histology; D051381:Rats; D012669:Seminal Vesicles / Q000033:anatomy & histology; D013737:Testis / Q000033:anatomy & histology; D013739:Testosterone / Q000494:pharmacology*; D013961:Thyroid Gland / Q000033:anatomy & histology; D013964:Thyroid Neoplasms / Q000209:etiology*
D009602:Nitrosamines; D013739:Testosterone; C012457:diisopropanolnitrosamine