THE EFFECT OF SEX HORMONES ON THE INCIDENCE OF EXPERIMENTAL URINARY BLADDER TUMORS IN RATS
1975 Volume 66 Issue 7 Pages 409-417
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1975 Volume 66 Issue 7 Pages 409-417
Recently, the incidence of bladder cancer has increased and many chemical substances have been suspected as carcinogens.
Clinically, it is well-known that incidence of human urinary bladder cancer (including papilloma) in female is lower than that in male, female to male ratio being only twenty to fourty per cent. It is also recognized that the urothelium is easily influenced by sex hormones.
The authors have studied the effects of testosterone propionate, estradiol and estriol on experimental bladder tumors induced in eight-week-old Wistar-Imamichi strain male rats by oral administration of 0.02mg/head/day of N-butyl-N-(4-hydroxybutyl)-nitrosamine as carcinogen for eight weeks (average total doses: 1.12mg).
The results were as follows:
1) In the group which was not treated for twelve weeks after completion of the carcinogen administration, six out of twenty-five cases showed bladder-tumors and two of twenty-five showed hyperplasia.
2) In the group which was injected intramuscularly 3mg/kg (body weight) of testosterone propionate (Enarmon-oil®) one time weekly from the beginning of the carcinogen administration through the twentieth week, nine out of twenty-three cases showed bladder tumors and two were with hyperplasia.
3) In the group which was injected intramuscularly 3mg/kg (body weight) of estradiol (Ovahormone benzoate®) one time weekly from the beginning of the carcinogen administration through the twentieth week, two out of twenty-three cases developed bladder tumors and five were with hyperplasia.
4) In the group which was injected intramuscularly 3mg/kg (body weight) of estriol (Estriel-depot®) one time weekly from the beginning of the carcinogen administration through the twentieth week, two out of twenty four cases showed bladder tumors and three were with hyperplasia.
5) In the group which was not treated for twenty weeks, none was with bladder tumor or hyperplasia.
There were significant difference between the testosterone propionate group and the estradiol group (p<0.02), and the testosterone propionate group and the estriol group (p<0.02) in the incidence of bladder tumor.
But there was not a significant difference between the testosterone propionate group and estriol group (p=2.704) in the incidence of bladder tumor or hyperplasia.
