In this paper, the life cycle assessment(LCA) methodology is applied to Personal Computer's basic materials in order to analyze the impact to the environment. LCA data collection is carried out taking into account on main materials of PC's parts and compo

This study was limited Gangwon-do's manufacturing companies that participated in the educational-industrial consortium. These companies' present status and activities under implementation identified and interpreted by this study, therefore, are insufficie

Endocrine disruptors have been concerned in toxicology but now challenged as physiological point especially concerned with exposing dose and period. In this study the low-dose chronic administration of di(2-ethylhexyl) phthaltae (DEHP) during reproductive period was examined to evaluate the possible roles. Adult male and female CD-1 mice were exposed to DEHP with drinking water containing 133 g/L and 1,330 ㎍/L DEHP in water according to OECD 433 guide line and sacrificed just after weaning. The weights of uterus and ovary were decreased by drinking of 1,330 ㎍/L DEHP water. There was not adverse effects on either accumulated mating rate and mating rate depend on estrus stage, pregnancy duration, and sex ration at birth. However, the accumulated rate of successful delivery and litter size were significantly high at 1,330 ㎍/L DEHP water. The number of epididymal sperm was significantly increased by drinking of 1,330 ㎍/L DEHP water. In addition, the number of follicles (primary, secondary, tertiary) were more many than control at 1,330 ㎍/L DEHP water drunk mother. Though further studies are needed to identify what are the mechanism of DEHP in folliculogenesis and spermatogenesis. From this study we firstly report the effect of low-dose chronic administration of DEHP with drinking could change the ovarian follicle population size and spermatogenesis rate. Put together, those finding is different from previous high-dose effects and suggest the physiological role of DEHP in gonads and uterus.

In the present study, we employed Hershberger assay to determine possible androgenic or antiandrogenic activities of three di-2-ethylhexyl phthalate (DEHP) substitute candidates. The assay was carried out using immature castrated Sprague–Dawley male rats. After 7 days of the surgery, testosterone propionate (TP, 0.4 mg/kg/day) and test materials (low dose, 40 mg/kg/day; high dose, 400 mg/kg/day) were administered for 10 consecutive days by subcutaneous (s.c.) injection and oral gavage, respectively. Test materials were DEHP, 2-ethylhexyl oleate (IOO), 2-ethylhexyl stearate (IOS) and triethyl 2-acetylcitrate (ATEC). The rats were necropsied, and then the weights of five androgen-dependent tissues [ventral prostate, seminal vesicle, coagulating glands, levator ani-bulbocavernosus (LABC) muscle, paired Cowper’s glands, and glans penis] and four androgen-insensitive tissues (kidney, adrenal glands, spleen and liver) were measured. All test materials including DEHP did not exhibit any androgenic activity in the assay. On the contrary, antiandrogen-like activities were found in all test groups, and the order of the intensity was ATEC < DEHP < ISO < IOO in the five androgen-sensitive tissues. There was no statistical difference between low dose treatment and high dose treatment of all replacement candidate groups. In DEHP groups, high dose treatment exhibited significant weight gains in LABC and Glan Penis. There was no statistical difference in androgen-insensitive tissue measurements. Since the effects of ATEC treatment on the accessory sex organs were much less or not present at all when compared to those of DEHP, ATEC could be a strong candidate to replace DEHP. IOO treatment brought most severe weight reduction in all of androgen-sensitive tissues, so this material should be excluded for further screening of DEHP substitute selection.

Bisphenol-A(BPA) is a member of alkylphenol family, and shows adverse effects including reduced fertility, reproductive tract abnormalities, metabolic disorder, cancer induction, neurotoxicity and immunotoxicity. In the present study, we conducted Hershberger assay to evaluate whether the two candidates to replace BPA have androgenic or antiandrogenic activity. The assay was carried out using immature castrated Sprague–Dawley male rats. After 7 days of the surgery, testosterone propionate (TP, 0.4 mg/kg/day) and test materials (low dose, 40 mg/kg/day; high dose, 400 mg/kg/day) were administered for 10 consecutive days by subcutaneous (s.c.) injection and oral gavage, respectively. Test materials were BPA, isosorbide (ISO) and cyclohexanedimethanol (CHDM). The rats were necropsied, and then the weights of five androgen-dependent tissues [ventral prostate, seminal vesicle, levator ani-bulbocavernosus (LABC) muscle, paired Cowper’s glands, and glans penis] and three androgen-insensitive tissues (kidney, spleen and liver) were measured. All test materials including BPA did not exhibit any androgenic activity in the assay. On the contrary, antiandrogen-like activities were found in all test groups, and the order of the intensity was CHDM > BPA > ISO in the five androgen-sensitive tissues. There was no statistical difference between low dose treatment and high dose treatment of BPA group as well as ISO group. In CHDM group, high dose treatment exhibited most severe weight reduction in all measured tissues. There was no statistical difference in androgen-insensitive tissue measurements, except BPA groups. Since the effects of ISO treatment on the accessory sex organs were much less or not present at all when compared to those of BPA, ISO could be a strong candidate to replace BPA. CHDM treatment brought most severe weight reduction in all of androgen-sensitive tissues, so this material should be excluded for further screening of BPA substitute selection.

Gonadotropins are heterodimers consisting an alpha chain (Cgα) and a beta chain. Interestingly, presence of complicated LH-β transcripts in rat testis was accidently found; testicular LH-β transcripts were confined in seminiferous tubules to spermatids, and the translated products were localized in the elongated spermatids. We hypothesized that mouse testis has potential to produce the tissue specific LH-β with similar structure to the rat testicular forms. To verify our hypothesis, we examined the adult mouse (ICR) testis using RT-PCR and immunohistochemistry. The PCR revealed the presence of the identical products in the reactions for three LH subunit types. The expected product sizes for mouse Cgα and LH-β known as pituitary type were 224 bp and 503 bp, respectively. The testicular type LH-β products were produced by a primer set based on the rat sequences, with unexpected size of 800 bp. Sequencing revealed that the proximal and distal parts (2-82 and 661- 773 bp, respectively) were homologous to rat testicular LH-β cDNA, and middle part (83-660 bp) was a unique mouse-specific region. Both Cgα and LH-β positive signals were in the round and elongated spermatids and mature sperms, and the LH-β signals were more intense. In conclusion, our study demonstrated that the presence and localization of the LH subunits in mouse testis. Further studies will be needed to understand the precise structure and function of mouse testicular LH.

Surgical castration (also known as orchidectomy, ORX) has been frequently performed to avoid uncontrolled breeding. However, it has some serious disadvantages. Several laboratories have developed chemical castration methods, using bilateral intratesticular injection (BITI) of simple chemical solutions. The present study was undertaken to compare the effects of ORX and of hypertonic saline BITI on the androgen-sensitive tissues such as pituitary and hypothalamus. Serum testosterone (T) levels of ORX animals and hypertonic saline BITI animals (SAL) after 4 weeks of the manipulations exhibited significantly drops as compared with the levels of intact animals (Intact:ORX:SAL = 7.74± 1.31:1.34±0.19:1.28±0.18 ng/ml, p<0.001). Both ORX and BITI method induced similar stimulatory effects on the pituitary gonadotropin subunits and hypothalamic KiSS-1 gene expressions. In contrast, the effects of ORX and hypertonic saline BITI on hypothalamic GnRH gene expression were different from these gene expressions, shown an inverse relationship between the two groups (Intact:ORX:SAL = 1:0.45±0.06:1:2.07±0.41:1.51±0.37 AU; ORX, p<0.001; SAL, p< 0.05). In conclusion, we provided evidence that hypertonic saline BITI method has equivalent efficacy of T depletion to surgical castration in rats. The present study suggests the hypertonic saline BITI could be a promising substitute to conventional surgical castration.

Nonylphenols (NP) are used in manufacturing antioxidants and lubricating oil additives, which are considered to be as potent endocrine disruptor. The aim of this study was to examine the effects of NP on reproductive system in adult male mice. Mice were divided into 4 groups; (1) tap water (CON group), (2) 50 μg/L (NP50), (3) 500 μg/L (NP500) and (4) 5000 μg/L (NP5000) of NP via the drinking water for 4 weeks. Mice were sacrificed and the reproductive organ weights were measured. The caudal epididymal sperms were count to assess the toxicity on germ cells. Histopathological changes of tissues were observed by using hematoxylin/eosin staining. The weights of testis in NP5000 group were significantly lighter than those in CON group (104.9±2.9 mg vs 90.7±5.1 mg, p<0.05). And weights of epididymis significantly increased in NP500 group (44.2±2.6 mg vs 54.42±3.44 mg, p<0.05). As concentration of NP increased, the number of sperms significantly decreased (NP50 and NP500, p<0.01; NP5000, p<0.001). In histopathological analyses, the sperms in seminiferous tubules showed a concentration-dependent decrease in mice treated with NP. In epididymis, treatment with NP resulted in empty space and the reduced sperm numbers in dose-dependent manner. Our results confirmed the dose-dependent decrease in the number of sperm and histopathological abnormality of testis and epididymis in mice exposed from 50 μg/L to 5000 μg/L of NP for 4 weeks. The present study suggests that oral exposure of NP might have negative effects on reproductive function, particularly on germ cells, in adult male mice.

Background & Objectives: Methoxychlor(MET), an organochlorine insecticide, has been thought a potent endocrine disrupting chemical. The present study was undertaken to examine whether short-term exposure to MET can alter the onset of puberty and the associated reproductive parameters such as hormone receptor expressions in prepubertal female rats. Method: MET (1, 10 and 100 mg/kg/day) was administered daily from postnatal day 25 (PND 25) through the PND 34, and the animals were sacrificed on the PND 35. The first V.O. day was monitored, and the weights of reproductive tissues were measured. To assess the structural alterations in the ovary and uterus, the tissues were embedded in paraffin and stained for histological analysis. The transcriptional activities of hypothalamic and pituitary genes were measured using quantitative RT-PCRs. The uterine and hypothalamic proteins were extracted and used for the ER western blotting. Results: As a result, 100 mg group showed advanced V.O. than control, 1 mg group and 10 mg group. The wet weights of ovaries from MET-treated animal dose-dependently increased. The uterine weights were increased in 1 mg group and 10 mg group, while the 100 mg group samples were not significantly different from control tissues. The adrenal, kidney, spleen and thymus weights were not shown any significant change. Corpora lutea and fully grown follicles were observed in the ovaries from the 100 mg group, while numerous primary and secondary follicles were observed in the ovaries from control group. Myometrial thickness of MET-treated group was dose-dependently increased. Epithelial hypertrophy and well-developed glands were observed in the uterus from the 10 mg groups. Conclusions: The present study demonstrated that the short-term exposure to MET during the critical period of prepubertal stage could activate a reproductive endocrine system, resulting the early onset of puberty in immature female rats. Our study suggests that MET’s disrupting effect might be derived from premature activation of key reproduction-related genes in hypothalamus-pituitary neuroendocrine circuit.

High-fructose corn syrup (HFCS) is widely used as sweetener, and its overconsumption is become a major health problem. In the present study, we used adult female rats and applied a 28 days HFCS feeding model to monitor the estrous cycle and changes in tissue weights and histology. Adult female rats were divided into three groups. Animals were fed with ad libitum normal chow and (1) 24 hours tap water (Control group), (2) 12 hours HFCS access during dark period and 12 hours tap water (12H group), and (3) 24 hours HFCS only access (24H group). Total exposure period was 28 days. There is no significant change in body weight between control and HFCS-fed animals. Both absolute and relative weights of ovary in 24H animals were significantly heavier than those in control or 12H animals. The absolute and relative weights of the kidney and liver in 24H groups were significantly heavier than those in control or 12H animals. The estrous cycles of the 24H animals were significantly longer. Histological analyses revealed that 24H ovaries were relatively bigger and possessed more corpus lutea than control ovaries. Uterine sections of 12H and 24H animals showed a well-developed stratum vasculare between inner and outer myometrial layers. The number of endometrial glands were decreased in 12H uteri, and recovered in 24H uteri compared to control. Numbers of convoluted tubule in distal region increased in 12H and 24H kidney samples. Liver specimens of 12H and 24H showed the increased number of fat containing vacuoles. In conclusion, our study demonstrated that HFCS treatment for 28 days could induce (1) changes in length of estrous cycle with extended estrous and diestrous stages, (2) altered ovarian and uterine histology, and (3) liver and renal lipid accumulation. These findings reveal the adverse effects of HFCS drinking on the reproductive function and lipid metabolism of female rats.

4-Nonylphenol (NP) is a surfactant that is a well-known and widespread estrogenic endocrine disrupting chemical (EDC). Although it has been known that the affinity of NP to ERs is low, it has been suggested that low-dose NP has toxicity. In the present study, the endocrine disrupting effects on reproduction, and the weight of gonads, epididymis, and uterus were evaluated with the chronic lower-dose NP exposing. This study was designed by following the OECD test guideline 443 and subjected to a complete necropsy. In male, NP had an effect on the weight of the testis and epididymis in both F0 and F1. In females, NP decreased the weight of ovary and uterus in F0 but not in pre-pubertal F1 pubs. Fertility of male and female in F0 or F1 was no related with NP administration. The number of caudal-epididymal sperm by body weight (BW) was not different between groups in both F0 and F1. Besides, the difference of the sperm number between generations was not detected. The number of ovulated oocytes was similar between groups in F0, but significantly decreased in NP 50 group of F1. The litter size and sex ratios of offspring in F1 and F2 were not different. The accumulated mating rate and gestation period were not affected by the NP administration. Those results shows that chronic lower-dose NP administration has an effect of endocrine disruptor on the weight of gonads and epididymis of F0 and F1 but not in reproduction. Based on the results, it is suggested that chronic lower-dose NP exposing causes endocrine disruption in the weight of gonad and epididymis but not in the reproductive ability of next generations.

Adipose tissue is one of the major endocrine gland. More recently, local production of steroids in adipocytes differentiated from mouse 3T3-L1 cell-line was reported. We hypothesized that rat adipocytes have steroidogenic machinery and the expression patterns of the components might be differentially regulated, depending on the distribution and sex. To verify this hypothesis, we collected the adipose tissues depot- and sex-specifically at postnatal day (PND) 30, and performed quantitative RT-PCRs. In overall aspects, the abundances of the transcripts were lower in the brown adipose of both sexes. 3β-HSD transcript levels in female abdominal and reproductive adipose, CYP17 transcript levels in female reproductive adipose, 17β-HSD transcript levels in female abdominal and reproductive adipose, and CYP19 transcript levels in female abdominal adipose were significantly lower than those of male counterparts. Similar to steroidogenic factors, the abundance of the ER-α transcripts were generally lower in the brown adipose of both sexes. ER-β transcripts were more abundant in male white adipose depots than their female counterparts. The levels of LHR transcripts in female reproductive adipose were significantly higher than those of male counterpart. In conclusion, our study demonstrated that the expressions of steroidogenesis-related genes were depot- and sex-specifically occurred in the immature male and female rat adipose tissues. Our study suggested that the adipose tissues are not only targets but de novo synthesizing sites of sex steroid(s), though the synthesizing activities could be much less than in gonads. Further researches in this field will be helpful for understanding the adipose physiology and for medical application such as sex-specific steroid supplement therapies for older populations.

Lipopolysaccharide (LPS), an endotoxin, elicits strong immune responses in mammals. Several lines of evidence demonstrate that LPS challenge profoundly affects female reproductive function. For example, LPS exposure affects steroidogenesis and folliculogenesis, resulting in delayed puberty onset. The present study was conducted to clarify the mechanism underlying the adverse effect of LPS on the delayed puberty in female rats. LPS was daily injected for 5 days (50 μg/kg, PND 25-29) to treated animals and the date at VO was evaluated through daily visual examination. At PND 39, animals were sacrificed, and the tissues were immediately removed and weighed. Among the reproductive organs, the weights of the ovaries and oviduct from LPS-treated animals were significantly lower than those of control animals. There were no changes in the weights of uterus and vagina between the LPS-treated and their control animals. Immunological challenge by LPS delayed VO. Multiple corpora lutea were found in the control ovaries, indicating ovulations were occurred. However, none of corpus luteum was present in the LPS-treated ovary. The transcription level of steroidogenic acute regulatory protein (StAR), CYP11A1, CYP17A1 and CYP19 were significantly increased by LPS treatment. On the other hand, the levels of 3β- HSD, 17β-HSD and LH receptor were not changed by LPS challenge. In conclusion, the present study demonstrated that the repeated LPS exposure during the prepubertal period could induce multiple alterations in the steroidogenic machinery in ovary, and in turn, delayed puberty onset. The prepubertal LPS challenge model used in our study is useful to understand the reciprocal regulation of immune (stress) - reproductive function in early life.

In mammals, puberty is a process of acquiring reproductive competence, triggering by activation of hypothalamic kisspeptin (KiSS)-gonadotropin releasing hormone (GnRH) neuronal circuit. During peripubertal period, not only the external genitalia but the internal reproductive organs have to be matured in response to the hormonal signals from hypothalamic-pituitary-gonadal (H-P-G) axis. In the present study, we evaluated the maturation of male rat accessory sex organs during the peripubertal period using tissue weight measurement, histological analysis and RT-PCR assay. Male rats were sacrificed at 25, 30, 35, 40, 45, 50, and 70 postnatal days (PND). The rat accessory sex organs exhibited differential growth patterns compared to those of non-reproductive organs. The growth rate of the accessory sex organs were much higher than the those of non-reproductive organs. Also, the growth spurts occurred differentially even among the accessory sex organs; the order of prepubertal organ growth spurts is testis = epididymis > seminal vesicle = prostate. Histological study revealed that the presence of sperms in seminiferous tubules and epididymal ducts at day 50, indicating the puberty onset. The number of duct and the volume of duct in epididymis and prostate were inversely correlated during the experimental period. Our RT-PCR revealed that the levels of hypothalamic GnRH transcript were increased significantly on PND 40, suggesting the activation of hypothalamic GnRH pulse-generator before puberty onset. Studies on the peripubertal male accessory sex organs will provide useful references on the growth regulation mechanism which is differentially regulated during the period in androgen-sensitive organs. The detailed references will render easier development of endocrine disruption assay.

Previous studies, including our own, have demonstrated that the intratesticular injection of hypertonic saline (20%) decreased serum testosterone level which was similar to the surgical castration in the rat, showing the state of chemical castration. In the present study, we further verify the efficacy of this less invasive method as an alternative of surgical orchidectomy in the andrological field. Sterilized 20% saline was directly injected into the adult male rats (750 μl per testis). The tested rats were divided into 3 groups including intact group (intact), orchidectomy group (ORX) and saline injection group (SAL) after bilateral orchidectomy was performed at the same day of injection. All rats were sacrificed at 4 weeks after injection. The reproductive organs (testes, epididymis, seminal vesicles and prostates) were collected and used for DNA and protein pattern analyses. Also, patho-histological studies on the testes were performed. In contrast to the intact group, similar DNA damages of testis and seminal vesicle were appeared in ORX group and SAL group. The DNA degradations seemed to be the results of necrosis rather than apoptosis. In the protein pattern analysis, all the testing tissues exerted similar patterns in the ORX group and the SAL group compared to the those of intact group. Patho-histological studies revealed that severe degenerative changes in testicular seminiferous tubules and massive infiltration of immune cells in SAL group. The present study confirmed that direct injection of hypertonic saline into the testis caused the equivalent biochemical changes in the accessory sex organs as shown in the orchidectomized animals. These results suggest that hypertonic saline injection model could be a useful castration model which can substitute for surgical castration when its safety is secured through further study in the future.

최근 고장성(20%) 생리식염수를 흰쥐 정소에 직접 주사할 경우, 혈중 테스토스테론 수준이 최저 수준에 도달하는 화학적 거세 상태에 들어감이 보고되었다. 본 연구는 이러한 간단한 생리 식염수 주사 모델의 효용성을 더 검증하기 위해 정소의 미세 해부 구조상의 변화를 조사하였다. 실험군으로는 무처리군(intact, control), 정소제거군(orchidectomy), 그리고 식염수 주사군(saline-injection)으로 하였으며, 식염수 주사군에는 정소당 750 ㎕의 멸균한 20% 식염수를 직접 주사하였다. 정소 제거 수술은 식염수 주사가 행해진 날에 시행하였다. 주사후 30일 경과 후에 동물을 희생하여 생식조직들을 채취하고 무게를 측정한 후 조직학적 조사를 위해 고정시켰다. 체중의 경우 무처리 대조군과 비교하여 정소절제군과 식염수 주사군 모두에서 유의한 변화는 없었다. 식염수 주사군의 정소 무게는 무처리 대조군에 비해 유의하게 감소하였다. 부정소와 저정낭의 무게의 경우 무처리 대조군에 비해 정소절제군과 식염수 주사군 모두에서 유의하게 감소하였으며, 전립선의 경우 무처리 대조군에 비해 정소절제군에서는 유의하게 감소하였으며, 식염수 주사군에서는 감소하는 경향은 있었지만 유의성은 없었다. 외양상으로 식염수 주사군의 정소에는 약간의 위축이 나타났으며, 백막이 정상적으로 보였다. 그러나 조직학적으로 정소 대부분에서 괴사가 발견되었으며, 헤마톡실린-에오신으로 거의 염색되지 않았다. 동일한 절편에서, 주사 부위의 정반대 부분은 비정상적인 세포층들이 염색되었다. 대부분의 세정관에서 미성숙한 생식세포들이 기질 막에서 분리되고, 내강 쪽으로 세포들이 떨어져 나간 것이 확인되었다. 본 연구는 정소내 고장성 식염수 직접 주사가 부속 생식기관에 정소절제와 유사한 테스토스테론 제거 효과를 유발할 수 있음을 확인하였다. 비록 심층적인 연구들이 더 요구되지만, 본 연구는 정소 내 고장성 식염수 직접 주사법이 비용이 덜 들고 덜 침습적이면서 정소절제술이나 화학적 거세와 거의 동일한 효용성을 가졌음을 시사한다.

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 (/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- (p<0.01) and FSH- (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.

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 p<0.001) compared to the control (PND ). 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.