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A long term experiment with Fischer-344 -rats was performed. The rats received the test substance in food for 103 weeks [0.05 or 0.1 % in diet (ca. 33 or 67 mg/kg/d)].
There was no significant positive association between the administered dose of 1.5-naphthylenediamine and mortality in either sex of the rats; in all groups adequate numbers of animals survived sufficiently long to be at risk from late-developing tumors (males: high dose: 37/50 = 74 %, low dose group: 40/50 = 80 %, control: 17/25 = 68 %; females: high dose: 38/50 = 76 %, low dose: 38/50 = 76 %, control: 26/25 = 64 %); the weight development of the dosed rats was comparable to controls; among dosed female rats, a statistically significant (p=0.003) increase in endometrial stromal polyps was diagnosed; several of these benign tumors underwent malignant transformation to stromal sarcomas; the incidence of female rats showing either adenoma or carcinoma of the clitoral gland was statistically significant (Cochran-Armitage test indicated a positive association between dose and tumors: p=0.003; Fischer exact test compared high dose to controls: p=0.021); for females the Fisher exact test comparing control to low dose for combined incidence of C-cell carcimoma of the thyroid had a probability level of p=0.46, a marginal result, not regarded as significant by the investigators; no neoplasms were observed at statistically significant increased incidences in treated male rats; the authors stated that based on lack of clinical signs or weight loss, the male rats may have been able to withstand a higher dose; under the conditions of this bioassay, the test substance was carcinogenic in female rats, causing clitoral and uterine neoplasms (NCI 1978).
Gold et al. calculated a median tumor-inducing dose (TD50) for the uterine neoplasms with 69.6 mg/kg (Gold 1986).
Hasemann published that benign stromal polyps were observed relative frequently as spontaneous tumors in Fisher 344 rats (Hasemann ...

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