Alteration in the Transcriptional Activities of the Hypothalamic-Pituitary Reproductive Axis in Peripubertal Female Rats

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: MON 515-547-Female Reproductive Endocrinology
Basic/Translational
Monday, June 17, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board MON-518
Eun Young Jeon1 and Sung-Ho Lee*2
1Sangmyung University, Seoul, South Korea, 2Sangmyung University, Seoul-City, South Korea
Activatiion of hypothalamic-pituitary-ovarian(H-P-O) axis initiates puberty in female mammals. However, the exact mechanism for the normal puberty onset has not been fully understood yet. The present study examined the activity changes in H-P-O hormonal axis from postnatal days (PND) 29 to PND 43. The wet weights of reproductive organs and serum sex steroid levels were measured. Histological studies on reproductive tissues were conducted. Semi-quantitative RT-PCRs were emplyed to examine the expression of hypothalamic and pituitary factors. Body weights increased by approximately 5g per day, and the rate of vaginal opening was highest(66%) at PND 37. Weights of the ovary, uterus and pituitary significantly increased from PND 37(p<0.01). Serum etrogen levels significantly increased on PND 39(p<0.01). Progesterone levels increased significantly on PND 35(p<0.05), but decreased on PND 37, then significantly elevated on PND 39(p<0.01). Histological studies revealed the gradual development of the ovarian follicles from PND 29. Uterine lining was gradually grown, and the well-developed luminal epitelial layers could be confirmed on PND 41. The GnRH mRNA levels fluctuated from PND 29 through PND 39, then increased significantly on PND 41(p<0.05) and PND 43(p<0.01). Kisspeptin expression pattern was similar to that of GnRH, showing significant increase from PND 41(p<0.01) and PND 43(p<0.01). GPR 54 levels decreased significantly from PND 29 to PND 35(p<0.01) and reached lowest level on PND 39(p<0.01), then significantly increased until PND 43(p<0.05). The GnIH levels fluctuated from PND 29 through PND 39, then increased two times compared to the lowest level on PND 41(p<0.05). The mRNA level of GPR147 gradually increased from PND 29, then increased significantly on PND 41(p<0.01) and PND 43(p<0.01). The expression of NeurokininB(Tac) increased significantly on PND 41(p<0.05) and PND 43(p<0.01). The changes in TacR3 expresion were not significant until PND 39, but increased significantly on PND 41(p<0.05) and PND 43(p<0.01). The transcriptional activity of pituitary Cgα appeared to be decrease on PND 35, then started to increase on PND 37, significantly increased on PND 39(p<0.05) and PND 43(p<0.01). The mRNA level of LH-β showed no change until PND 39 but significantly increased on PND 43(p<0.01). Expression of FSH-β increased significantly on PND 37(p<0.05) and PND 43(p<0.01). The present study shows dynamic changes in gene expression of the H-P hormonal axis in peripubertal female rats. Simultaneously, this study demonstrates that the peripubertal expression patterns of acceleration/inhibition factors in the hypothalamic GnRH pulse generation system were not comparable with those in adults. Based on the results, one can postulate that the combination of the regulatory factors which controls the onset of puberty seem to be different from those control estrous cycle in adulthood.

Nothing to Disclose: EYJ, SHL

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

Sources of Research Support: This work was supported by the National Research Foundation of Korea Grant funded by the Korean Government (NRF-2009-0077004 and NRF-2011-0025490).