• Journal of Veterinary Clinics
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• v.17 no.1
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• pp.285-288
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• 2000

Nine immature 30-day-old female rats were injected sc at 0800 hr with pregnant mare serum gonadotrophin(PMSG) to induce ovulation and mating. Fifty-six hours later the animals were placed with mature male rats overnight (one female and one male). Five of 9 immature female rats treated with PMSG were pregnant and allowed to maintain the pregnancy to term. Three of 5 pregnant rats were failed to maintain pregnancy to term. Two of 5 pregnant rats seemed to be developed normally and increased abdominal enlargement as pregnancy progresses, but did not occurred parturition on day of 43 or 48 of pregnancy, respectively. On day 44 or 49, pregnant rats were killed and examined uterus and ovaries. There was no fetus but approximately 50∼60ml. of mucopurulent fluids were accumulated in the uterine cavity and 40 or 42 corpora lutea persisted in the ovaries. Pyometra was developed after coitus in PMSG-treated immature female rat.

• Toxicological Research
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• v.16 no.3
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• pp.201-209
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• 2000

In association with the international validation program to establish a rodent uterotrophic assay, we conducted preliminary uterotrophic assay proposed by GECD using immature female rats. In the present study, oral and subcutaneous routes were chosen to compare the effects of estrogenic com-pounds in the two dosing regimens. The reference compound ethinyl estradiol (EE) and the antagonist ZM189154(ZM) were administered by gavage or subcutaneously (s.c.) to immature female SD rats from 20 to 22 days of age. For each study, sixty-six female rats were randomly assigned to eleven groups: Untreated control, EE 0,0.01, 0.03, 0.1, 0.3, 1.0,3.0 and 10.0 $\mu\textrm{g}$/kg, EE 3.0 $\mu\textrm{g}$/kg(gavage)/0.3 $\mu\textrm{g}$/kg(s.c) & ZM 0.1 mg/kg, and EE 3.0 $\mu\textrm{g}$/kg(gavage)/0.3 $\mu\textrm{g}$/kg (s.c) & ZM 1.0 mg/kg. There were no treatment-related changes in clinical signs, body weights, food consumption, and necropsy findings in any groups of two studies. The wet and blotted uterus weights increased dose-dependently. Histopathological examination revealed that diameter of uterine duct, height of uterine luminal epithelium. and height oj vaginal epithelium increased dose-dependently. The proliferating cell nuclear antigen (PCNA) immunoreactive cells were increased in number dose-dependently. The estrogenic effects observed in the present studies occurred at $\geq$ 0.3 $\mu\textrm{g}$/kg of oral dose and $\geq$ 0.1 $\mu\textrm{g}$/kg of s.c. dose. An antagonistic effect of ZM against EE was found in both uterus weight and histopathological parameters. From the results obtained, it can be concluded that dose-dependence of the uterotrophic assay using EE and ZM was well demonstrated by gavage and subcutaneous administration and that the estrogenic effects of EE by s.c. dose were higher than those by gavage administration. In addition, blotted uterus weight was more sensitive than wet uterus weight and vaginal epithelial height was found to be the most sensitive parameter among the parameters examined.

• Development and Reproduction
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• v.16 no.4
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• pp.295-300
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• 2012

Manganese ($Mn^{2+}$) is a trace element that is essential for normal physiology, and is predominantly obtained from food. Several lines of evidence, however, demonstrated that overexposure to $MnCl_2$ exerts serious neurotoxicity, immunotoxicity and developmental toxicity, particularly in male. The present study aimed to evaluate the effect of 0, 1.0, 3.3, and 10 mg/kg/day doses of $MnCl_2$ on the reproductive organs in the immature female rats. Rats (PND 22; S.D. strain) were exposed to $MnCl_2$ ($MnCl_2{\cdot}4H_2O$) dissolved in drinking water for 2 weeks. The animals were sacrificed on PND 35, then the tissues were immediately removed and weighed. Histological studies were performed using the uteri tissue samples. Serum LH and FSH levels were measured with the specific ELISA kits. Body weights of the experimental group animals were not significantly different from those of control group animals. However, ovarian tissue weights in 1 mg and 3.3 mg $MnCl_2$ dose groups were significantly lower than those of control animals (p<0.05 and p<0.01, respectively). Uterine tissue weights of 3.3 mg dose $MnCl_2$ groups were significantly lower than those of control animals (p<0.01), while the 1 mg $MnCl_2$ dose and 10 mg $MnCl_2$ dose failed to induce any change in uterine weight. Similarly, only 3.3 mg $MnCl_2$ dose could induce the significant decrease in the oviduct weight compared to the control group (p<0.05). Non-reproductive tissues such as adrenal and kidney failed to respond to all doses of $MnCl_2$ exposure. The uterine histology revealed that the $MnCl_2$ exposure could affect the myometrial cell proliferation particularly in 3.3 mg dose and 10mg dose group. Serum FSH levels were significantly decreased in 1mg $MnCl_2$ dose and 10 $MnCl_2$ mg groups (p<0.05 and p<0.01, respectively). In contrast, treatment with 1 mg $MnCl_2$ dose induced a significant increment of serum LH level (p<0.05). The present study demonstrated that $MnCl_2$ exposure is capable of inducing abnormal development of reproductive tissues, at least to some extent, and altered gonadotropin secretions in immature female rats. Combined with the well-defined actions of this metal on GnRH and prolactin secretion, one can suggest the $Mn^{2+}$ might be a potential environmental mediator which is involved in the female pubertal process.

• Development and Reproduction
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• v.13 no.3
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• pp.183-190
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• 2009

In mammals, puberty is a dynamic transition process from infertile immature state to fertile adult state. The neuroendocrine aspect of puberty is started with functional activation of hypothalamus-pituitary-gonadal hormone axis. The timing of puberty can be altered by many factors including hormones and/or hormone-like materials, social cues and metabolic signals. For a long time, attainment of a particular body weight or percentage of body fat has been thought as crucial determinant of puberty onset. However, the precise effect of high-fat (HF) diet on the regulation of hypothalamic GnRH neuron during prepubertal period has not been fully elucidated yet. The present study was undertaken to test the effect of a HF diet on the puberty onset and hypothalamic gene expressions in immature female rats. The HF diet (45% energy from fat, HF group) was applied to female rats from weaning to around puberty onset (postnatal days, PND 22-40). Body weight and vaginal opening (VO) were checked daily during the entire feeding period. In the second experiment, all animals were sacrificed on PND 36 to measure the weights of reproductive tissues. Histological studies were performed to assess the effect of HF diet feeding on the structural alterations in the reproductive tissues. To determine the transcriptional changes of reproductive hormone-related genes in hypothalamus, total RNAs were extracted and applied to the semi-quantitative reverse transcription polymerase chain reaction (RT-PCR). Body weights of HF group animals tend to be higher than those of control animals between PND 22 and PND 31, and significant differences were observed PND 32, PND 34, PND 35 and PND 36 (p<0.05). Advanced VO was shown in the HF group (PND $32.8{\pm}0.37$ p<0.001) compared to the control (PND $38.25{\pm}0.25$). The weight of ovaries (p<0.01) and uteri (p<0.05) from HF group animals significantly increased when compared to those from control animals. Corpora lutea were observed in the ovaries from the HF group animals but not in control ovaries. Similarly, hypertrophy of luminal and glandular uterine epithelia was found only in the HF group animals. In the semi-quantitative RT-PCR studies, the transcriptional activities of KiSS-1 in HF group animals were significantly higher than those from the control animals (p<0.001). Likewise, the mRNA levels of GnRH (p<0.05) were significantly elevated in HF group animals. The present study indicated that the feeding HF diet during the post-weaning period activates the upstream modulators of gonadotropin such as GnRH and KiSS-1 in hypothalamus, resulting early onset of puberty in immature female rats.

• Toxicological Research
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• v.18 no.4
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• pp.393-396
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• 2002

This study was carried out to evaluate the ostrogenic/antiandrogenic activity of Puerariae Radix in Sprague-Dawley rats. It has known that diverse phytoestrogen were included in some Puerariae Radix, especially in Pueraria mirifica. The Uterotrophic assay and Hershberger assay were performed to evaluate the ostogenic/antiandrogenic activity of various Puerariae Radix (Pueraria thunbergiana, Pueraria mirifica and Butea superba). In Uterotrophic assay, the extracts of Puerariae Radix were administered subcutaneously to immature female SD rats from 19 to 21 days of age. The wet uterus and vaginal weighs significantly increased in the group only treated with extracts of Pueraria mirifica. But, in Hersh-berger assay, all extracts of Puerariae Radix did not show any effects in the castrated rats. These results suggest that Pueraria mirifica has not undrogenic/antiandrogenic effect but potent estrogenic effect. It is possible that components of Pueraria mirifica may act as endocrine disruptor in human body.

• Proceedings of the Zoological Society Korea Conference
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• 1996.04a
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• pp.43.2-43
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• 1996

No Abstract, See Full Text

• Development and Reproduction
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• v.14 no.1
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• pp.35-41
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• 2010

Mammalian reproduction is regulated by a feedback circuit of the key reproductive hormones such as GnRH, gonadotropin and sex steroids on the hypothalamic-pituitary-gonadal axis. In particular, the onset of female puberty is triggered by gain of a pulsatile pattern and increment of GnRH secretion from hypothalamus. Previous studies including our own clearly demonstrated that genistein (GS), a phytoestrogenic isoflavone, altered the timing of puberty onset in female rats. However, the brain-specific actions of GS in female rats has not been explored yet. The present study was performed to examine the changes in the activities of GnRH neurons and their neural circuits by GS in female rats. Concerning the drug delivery route, intracerebroventricular (ICV) injection technique was employed to eliminate the unwanted actions on the extrabrain tissues which can be occurred if the testing drug is systemically administered. Adult female rats (PND 100, 210-230 g BW) were anaesthetized, treated with single dose of GS ($3.4{\mu}g$/animal), and sacrificed at 3 hrs post-injection. To determine the transcriptional changes of reproductive hormone-related genes in hypothalamus, total RNAs were extracted and applied to the semi-quantitative reverse transcription polymerase chain reaction (RT-PCR). ICV infusion of GS significantly raised the transcriptional activities of enhanced at puberty1 (EAP-1, p<0.05), glutamic acid decarboxylase (GAD67, p<0.01) which are known to modulate GnRH secretion in the hypothalamus. However, GS infusion could not change the mRNA level of nitric oxide synthase 2 (NOS-2). GS administration significantly increased the mRNA levels of KiSS-1 (p<0.001), GPR54 (p<0.001), and GnRH (p<0.01) in the hypothalami, but decreased the mRNA levels of LH-$\beta$ (p<0.01) and FSH-$\beta$ (p<0.05) in the pituitaries. Taken together, the present study indicated that the acute exposure to GS could directly activate the hypothalamic GnRH modulating system, suggesting the GS's disrupting effects such as the early onset of puberty in immature female rats might be derived from premature activation of key reproduction related genes in hypothalamus-pituitary neuroendocrine circuit.

• Korean Journal of Veterinary Research
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• v.25 no.2
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• pp.187-195
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• 1985

The Present study has been carried out to elucidate the antiestrogenic effects of tamoxifen in uteri of immature rats. Immature female Sprague-Dawley rats were allocated into 4, groups and injected with $5{\mu}g$ of estradiol-$17{\beta}$, $50{\mu}g$ of tamoxifen, a combination of both or vehicle only subcutaneously three times after an interval of 24 hours respectively. The concentrations, of cytosol estradiol receptor in uterus were measured by DCC method before and 1, 3, 6, 12, 24, 48 and 72 hours after the above treatments and those of nuclear estradiol were measured by protamine exchange method 72 hours and those of nuclear estradiol were measured by protamine exchange method 72 hours after the above treatments. The results obtained were summarized as follows: 1. The binding affinity of tamoxifen to estradiol receptor in uterine cytosol was lower than that of estradiol-$17{\beta}$, accordingly the translocation of estradiol receptor into the nucleus was found to be delayed. 2. Tamoxifen caused the retention of estradiol receptor in nucleus over 24 hours and inhibited the replenishment of the receptor from nucleus to cytosol in uterus.

• The Korean Journal of Zoology
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• v.19 no.1
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• pp.7-14
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• 1976

The release of ovulatory level of LH from the pituitary gland occurred between 51 and 56 hours after PMS treatment in 24-day old female rats. Estradiol given simultaneously with PMS advanced LH release 24 hours. Injections of estradiol $(2.5\\sim 40\\mu g)$ at 0, 24 and 48 hours failed to increase pituitary LH level by 51 hours after the first injection in ovariectomized rats. However, $5 \\mu g$ estradiol at 0, 24 and 48 hours followed by 1 mg progesterone at 48 hours elevated pituitary L level by 51 hours in ovariectomized rats. These results indicate that advancement of PMS-induced ovulation by estradiol in the previous study occurred by means of inducing premature release of LH and estrogen might synergize with progesterone in the regulation of LH in the pituitary gland.

• Journal of Veterinary Clinics
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• v.24 no.4
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• pp.563-567
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• 2007

This study evaluated the effect of ANTORIN R-10(pFSH), a commercially available follicle stimulating hormone on ovarian morphology, on follicular development and serum estradiol levels in rats. Immature female Wistar S/T rats(27 day old; 80-100 g B.wt) maintained under controlled environmental conditions($22{\pm}2^{\circ}C$; 50% humidity; 12 h light/12 h dark cycle) with free access to standard laboratory feed and tap water were utilized. Animals were allowed to acclimatize to the new environment for at least 2 weeks before being included in the experiment. Rats were randomly allotted to 5 groups(Control, SL 0.1AU, SH 0.2AU, TL 0.1AU and TH 0.2AU). ANTORIN R-10 was subcutaneously injected twice daily for 3 days. Twenty hours after hormone treatment, blood was collected to estimate the serum estradiol $17-\beta$ concentration. Immediately, all rats were sacrificed and the ovarian morphology, ovary weight and number of follicles were recorded. Ovaries were fixed for histomorphological examination. Higher standard and treatment groups were significantly increased on ovary weight and the number of follicles more than 1mm compared with lower standard and treatment. However, no difference revealed between standard and treatment groups. ANTORIN R-10 was similar effects of follicles development and maturation compared with House standard FSH.