Study on the Gonadotropin Receptors Expression in the Reproductive Endocrine System

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This research has been started for clarifing the behavior of the peptide hormone receptors on the hormone target organs in the reproduction endocrine system of the vertebrate, and got following results :1) THE EFFECT OF THE GnRH ON THE DEVELOPMENT OF GONADOTROPES : Pituitary primordia from rat fetuses were cultured with or without 10-9 M GnRH during the first 24 h of the culture, and the hormone synthesis and releasing were analyzed. The results suggest that pituitary primordia at 13.5 days of gestation are capable to respond to GnRH,and that GnRH is effective in stimulating the responsiveness of gonadotropes to GnRH during early pituitary cytodifferentiation.2) CLONING AND EXPRESSION OF THE RAT GnRH RECEPTOR mDNA : A rat GnRH cDNA was cloned with 1317 bp from a pituitary cDNA library. This clone had a full amino acid coding region, with 172 and 161 bp noncoding sequences in 5'-and 3'-flanking regions of the coding region, respectively. Then the receptor mRNA expression was analyze in … More rat pituitary during estrous cycle and after ovariectomy. The mRNA was expressed only in the gonadotropes. The mRNA level was significantly smaller in estrus than in other phases of the cycle. In ovariectomized rats, the mRNA expression was significantly increased 4 days after the operation, and maintained until 21 days after ovariectomy.3) GnRH RECEPTOR EXPRESSION IN THE OVARY : In the ovary, GnRH receptor was highly expressed on the healthy Graafian and preovulatory follicles with intense signals in their mural granulosa cells. Corpora lutea showed weak signals, but luteinizing follicles probably after atresia exhibited signals of moderate intensity. These data suggest that the GnRH receptor is involved in the various ovarian functions including follicular deveolopment, atresia, ovulation, and luteinization after ovulation and follicular atresia.4) CHARACTERIZATION OF THE HORMONE BINDING DOMAIN OF THE GONADOTROPIN RECEPTOR IN VARIOUS ANIMALS : For this study, we disigned several pairs of PCR primers which could amplify the domain from various animal species. After RT-PCR,the nucleotide and amino acid sequences were analysized. The values of homology of LH or FSH receptors between mammal and avian were always higher than those of their ligand hormone, suggesting that the hormone and receptor were evolved with strong interaction, and receptor was more conservative than ligand.5) EFFECTS OF CRYPTORCHIDISM ON THE EXPRESSION OF GONADOTROPIN RECEPTOR mRNA : Expression patterns of mRNAs of FSH and LH receptors were examined by Northern blot in adult rat testes after induction of unilateral cryptorchidism. At 4 weeks after the operation, signals were markedly increased in both receptor mRNAs in the abdominal testes as compared to those in the scrotal testes. There was also a remakable change in size pattern of LH receptor transcripts. This finding suggest that the expression of LH receptor mRNA is regulated locally within testis. Less