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.

INTRODUCTION
 MATERIALS & METHODS
  1. Animals
  2. Experimental design
  3. Histology
  4. Total RNA extraction and reverse transcriptasePCR analyses
  5. Statistical analysis
 RESULTS
  1. Changes in the body weights and the day ofvaginal opening
  2. Changes in the tissue weights
  3. Ovarian and uterine histology
  4. RT-PCRs of ovarian steroidogenesis-related transcripts
 DISCUSSION
 REFERENCES

• Da Kyung Yoo(Dept. of Life Science, Sangmyung University, Seoul 03016, Korea)
• Sung-Ho Lee(Dept. of Life Science, Sangmyung University, Seoul 03016, Korea) Corresponding Author