The purpose of this study was to decide the appropriate administration period in uterotrophic assay and to evaluate the usefulness of uterotrophic assay using two typical estrogen agonists and one antagonist, when chemicals were given orally. Diethylstilbestrol (DES), ethynyl estradiol (EE), or Atrazine (ATZ) was administered to immature Crj: CD (SD) IGS rats orally at doses of 0.01-1 μg/kg/day, 0.06-6 μg/kg/day, or 0.5-50 mg/kg/day from postnatal day (PND) 21 for 3 or 7 days, respectively. Additional groups of rats given ATZ orally at the above doses were also treated with 17β-estradiol (E2) subcutaneously at a dose of 0.3 μg/rat/day. A vehicle control group given only olive oil was established in each study, and a group given only E2 was included in the study of ATZ also. No abnormal clinical signs were detected in any of the groups. There were no significant differences in body weight between the vehicle control and each of the groups given DES, EE or ATZ, or the group given only E2 and each of the groups given ATZ plus E2. Premature vaginal opening was observed from 6 days in all rats given 6 μg/kg EE or ATZ plus E2. Uterine fluid was also present in all rats given 6 μg/kg EE or ATZ plus E2 for 3 or 7 days. Uterine weight was significantly higher in the rats given 1 μg/kg DES for 3 days and 6 μg/kg EE for 3 or 7 days, but no increases were detected in any of the rats given DES for 7 days. Although uterotrophic activity was not detected in any of the rats given only ATZ, co-treatment with 50 mg/kg ATZ and E2 for 3 days reduced the E2-induced increases in uterine weight. The present results demonstrated that the appropriate period of oral administration for detecting the estrogenic properties of DES and EE or anti-estrogenic properties of ATZ using the immature rat uterotrophic assay was 3 days and ATZ exerted weak anti-estrogenic effects on the uterus.
Mammary gland development and hyperprolactinemia of rats were induced by estradiol (E2) treatment. The condition of the animals resembled that of during lactation. When it focused on high PRL levels, we studied the molecular phenotype of the rat mammary gland following E2 treatment, targeting prolactin (PRL) mRNA, using the sensitive techniques of solution and in situ reverse transcriptase-polymerase chain reaction (RT-PCR). In addition, we compared the PRL mRNA and plasma PRL level with those in the mammary glands of both pregnant and lactating rats. In the E2-treated groups, the plasma PRL levels were increased. No mammary PRL mRNA was detected in E2-treated rats by either solution or in situ RT-PCR. The plasma PRL level was extremely high and associated with the mammary gland development in lactating rats. In addition, mammary PRL mRNA was detected in both pregnancy and lactation by solution and in situ RT-PCR. These results suggested a lack of PRL mRNA in the mammary gland of E2-treated rats, despite similar plasma PRL levels and morphological changes to those in lactating rats. The induction of PRL mRNA coincident with the development of mammary gland in the pregnant and lactating rats, differed from that in the E2-treated rats in molecular biology, particularly in PRL mRNA expression, and suggested that PRL mRNA in mammary gland contributes to de novo synthesis of PRL in milk which is under the multihormonal regulation.
The purpose of the present study was to determine whether or not salt excess might increase systemic blood pressure, proteinuria, and progress glomerulosclerosis based on morphometric image analysis in the subtotally nephrectomized rats. Experiments were performed on twelve 6-week-old male Wistar rats weighing 200-250 g. Eight rats received 5/6 nephrectomy and after surgery, these rats were divided into the following 2 groups consisting of 4 rats each: Sham-operation group was given standard water without salt to drink and salt treatment group was given 1% NaCl solution to drink for two weeks. In this remnant kidney model, salt loading was slightly effective in elevating blood pressure and induced significant increases in urinary protein excretion and urinary volume and enhanced glomerular sclerosis. The present results suggest that in the early stage of rat remnant kidney model, salt loading accelerates glomerular alterations with renal dysfunction.
Spontaneous proliferative pulmonary lesions were found in 10 (6 males and 4 females) of 244 (122 of each sex) transgenic (Tg) mice carrying the human prototype c-H-ras gene (rasH2). The pulmonary lesions included 2 bronchiolo-alveolar hyperplasias (BAHs), 2 bronchiolo-alveolar adenomas (BAAs), and 2 bronchiolo-alveolar adenocarcinomas (BACs) in males and 1 BAH and 3 BACs in females. The mutation patterns of the human c-H-ras codon 61 and endogenous mouse c-K-ras codons 12, 13, and 61 in these proliferative pulmonary lesions were analyzed by DNA amplification using polymerase chain reaction, single-strand conformation polymorphism (PCR-SSCP), and oligonucleotide dot blot hybridization. Two of the 3 BAHs, 1 of the 2 BAAs, and 5 of the 5 BACs had a CAG to CTG transversion at codon 61 of the human c-H-ras gene but no point mutations were detected in codons 12, 13, or 61 of the mouse c-K-ras gene. Immunohistochemically, no overexpression of p53 protein, hsp70 or mdm2 gene protein was detected in any of the lesions. These findings suggest that, at least, a point mutation of the human c-H-ras transgene may be an important step in progression of spontaneous lung tumors, whereas p53 abnormality may not play an important role of the pulmonary carcinogenesis in rasH2 Tg mice.
We studied the comparative changes in weight of the accessory sex organs in intact and castrated rats to which 17α-methyltestosterone (MT) had been administered. In study 1, MT was administered to SD rats at doses of 0.1, 1, and 10 mg/kg/day. In castrated rats that received oral administration, the ventral prostate was heavier in those given 1-10 mg/kg, while in intact rats the increase of this organ was not observed. In castrated rats that received subcutaneous injections, the bulbo cavernous/levator ani muscle (BC/LA) was heavier in intact rats given 1-10 mg/kg, while in castrated rats, BC/LA was heavier at all doses of MT. In study 2, MT was administered subcutaneously to SD rats at doses of 0.001, 0.01, and 0.1 mg/kg/day. The ventral prostate, seminal vesicle, and BC/LA were heavier in castrated rats given 0.1 mg/kg, while the only increase in intact rats was in the BC/LA of those given 0.1 mg/kg. In study 3, MT was administered orally to AP rats at doses of 25 and 100 mg/kg/day. The prostate and BC/LA were heavier in intact rats given 25 and 100 mg/kg, and in those intact rats given 100 mg/kg, the Cowper’s glands and seminal vesicle were heavier. In castrated rats, all organs were heavier in 25 and 100 mg/kg groups. This study demonstrates that treatment of intact and castrated rats induces changes in the weights of the accessory sex organs, and that castrated rats are more sensitive to MT than are intact rats.
This study was conducted as part of an international evaluation on transgenic mouse models as potential alternatives to the standard two-year bioassay. Methapyrilene hydrochloride (MP), a non-genotoxic rat-specific hepatocarcinogen, in the diet was given to male and female transgenic CB6F1 mice carrying copies of a human prototype c-Ha-ras gene (rasH2 mice) at doses of 0, 1, 750, 3, 500, and 7, 000 ppm and to male and female non-transgenic littermates (non-Tg mice) at 0 and 7000 ppm for 26 weeks and subsequently sacrificed. N-methyl-N-nitrosourea (MNU) was used as a positive control compound to confirm that a positive response is elicited in the rasH2 model. Complete autopsies were performed and all organs of mice were histologically examined. Lung alveolar/bronchiolar adenomas and carcinomas, a thymic lymphoma, splenic hemangiosarcomas, skin squamous cell papillomas/carcinomas and hemangiosarcoma, a Harderian gland adenoma, and uterus and testicular hemangiosarcomas were detected in rasH2 mice receiving MP or basal diet. Only one neoplasm was found in the non-Tg group, in a non-treated male. However, there were no effects of MP on tumor incidence or multiplicity, although rasH2 mice were sensitive to the carcinogenic activity of MNU. Slight hepatotoxicity, as evidenced by hepatocyte hypertrophy and small bile duct proliferation, was noted in rasH2 and non-Tg mice treated with MP, but no hepatic foci were noted in any mice. The results indicate that negative carcinogenicity of MP was confirmed even at doses higher than those employed earlier in B6C3F1 mice, and suggest that this non-genotoxic rat specific carcinogen may not be a human carcinogen. Thus, the rasH2 mouse model has utility as an alternative for the detection of carcinogenicity of environmental chemicals.
Histologic and morphometric variations in the thyroid glands were investigated in twenty normal Cynomolgus monkeys. Heterogeneity in the pattern of colloid staining and the appearance of degenerating cells were frequently observed in the lumina of the thyroid follicles (45 and 50%, respectively). A few animals showed so-called ‘palpation thyroiditis’, characterized by numerous degenerating cells in the lumina of many follicles accompanied by multi-focal epithelial cell degeneration and interstitial inflammatory reactions. The size of the follicular lumina was different among animals and within an individual thyroid gland. Males usually had larger follicles than females.
Apoptotic index (AI) of the gastrointestinal mucous epithelia was examined in mice at 8, 16, 24 and 48 hours after oral inoculation (HAI) of T-2 toxin (10mg/kg). In the fundic region of the stomach, AI prominently increased at 8 HAI and deceased thereafter in the foveolae gastricae while it started to increase slowly and became prominent at 24 HAI in the glandular base. AI in the glandular neck was constantly low. On the other hand, in the intestinal crypt epithelia, AI prominently increased at 8 HAI in all regions examined (duodenum, ileum, cecum and colon), and thereafter decreased with the lapse of time. AI was clearly higher in the small intestine than in the large one especially in the early stage. Mitotic index (MI) examined was drastically decreased at 8 HAI when AI prominently increased, and thereafter turned to recover in the lapse of time. However AI after T-2 toxin inoculation was not always proportional to MI before T-2 toxin inoculation. The sequence of and the regional difference in AI in the gastrointestinal mucous epithelia after T-2 toxin intoxication was first clarified in the present study.