Expression of gonadotropin releasing hormone (GnRH) has been described in the rate ovary. It remains, however, unkown whether GnRH is synthesized as a prohormone. Therefore, this study was performed to verify the expression of pro-GnRH by in situ
hybridization and further to investigate the effect of gonadotropin on GnRH or GnRH mRNA in rat ovary by immunohistochemical and in situ hybridization technique.
Adult female Sprague-Dawely rats were used and the estrous cycle was synchronized by intraperitoneal injection of pregnant mare's serum gonadotropin (PMSG). Ovaries were fixed with 4% paraformaldehyde and embedded with O.C.T. compound and cut by
cryostat. For immunohistochemistry, avidin-biotin peroxidase complex (ABS) method was employed and for in situ hybridization, 35S-end labeled oligonucleotide was used and followed by autoradiography.
By in situ hybridization using GnRH oligomer and GAP (GnRH associated protein) oligomer, GnRH or GnRH mRNA signals in the ovary increased by human chorionic gonadotropin (hCG) injection. At the 3 and 6 after hCG injection, the number of GnRH and
GnRH
mRNA containing cells increased rapidly and the density of GnRH and GnRH mRHA culminated at 9 hrs after hCG injection. With the follicular development, the high expression of GnRH and GnRH mRNA was also observed within the follicles. After
ovulation,
the density of GnRH or GnRH mRNA decreased in the follicles but increased in the corpus lutea.
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