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Regulation of gonadotropin-releasing hormone (GnRH) receptor messenger ribonucleic acid and GnRH receptors during the early preovulatory period in the ewe.
- Source :
-
Endocrinology [Endocrinology] 1994 Oct; Vol. 135 (4), pp. 1353-8. - Publication Year :
- 1994
-
Abstract
- Estradiol increases the number of GnRH receptors in the ewe. Although results from studies conducted in vitro indicate that progesterone may have a negative influence on the number of ovine GnRH receptors, this effect of progesterone has not been documented in vivo. To explore the regulation of GnRH receptors at the level of gene expression, a partial complementary DNA (cDNA) encoding ovine GnRH receptor was isolated using reverse transcription and polymerase chain reaction methodology. This partial cDNA (701 basepairs) was used to isolate a full-length cDNA encoding GnRH receptor from an ovine pituitary cDNA library. Northern blot analysis of RNA from ovine pituitary glands using the partial cDNA as a molecular probe revealed four messenger RNA (mRNA) transcripts at 5.6, 3.8, 2.1, and 1.3 kilobases. In some samples, a fifth transcript at 0.8 kilobases was also evident. GnRH receptor mRNA was not detected in ovine brain, heart, kidney, adrenal, or liver tissues. To examine the regulation of GnRH receptor mRNA and GnRH receptors during the early preovulatory period, relationships among steady state concentrations of GnRH receptor mRNA, numbers of GnRH receptors, and circulating concentrations of progesterone and estradiol during luteolysis were characterized. We hypothesized that during luteolysis, decreased concentrations of progesterone would be associated with increased concentrations of GnRH receptor mRNA and increased numbers of GnRH receptors. On day 11 or 12 of the estrous cycle, luteolysis was induced in 14 ewes by treatment with prostaglandin F2 alpha (PGF2 alpha). Four ewes were treated with saline (saline controls). Anterior pituitary tissue was collected 4 h (n = 4), 12 h (n = 5), and 24 h (n = 5) after treatment with PGF2 alpha or 24 h after treatment with saline and from four untreated ewes on day 11 or 12 of the estrous cycle (untreated controls). Twelve hours after treatment with PGF2 alpha, circulating concentrations of progesterone had decreased (P < 0.05) to 46% of the control values; however, concentrations of estradiol were not different from those in control ewes. Concentrations of GnRH receptor mRNA increased 2-fold during luteolysis and were higher than control values 12 h after PGF2 alpha treatment (P < 0.05). This increase in GnRH receptor mRNA was not accompanied by an increase in the number of GnRH receptors. Twenty-four hours after treatment with PGF2 alpha, concentrations of progesterone in PGF2 alpha-treated ewes had decreased (P < 0.05) to 15% of control values, whereas concentrations of estradiol had increased (P < 0.05) to 321% of control values.(ABSTRACT TRUNCATED AT 400 WORDS)
- Subjects :
- Animals
Base Sequence
Blotting, Northern
DNA analysis
DNA genetics
Dinoprost pharmacology
Dose-Response Relationship, Drug
Estradiol blood
Estradiol pharmacology
Female
Follicular Phase blood
Gene Expression Regulation
Molecular Sequence Data
Pituitary Gland, Anterior chemistry
Pituitary Gland, Anterior drug effects
Pituitary Gland, Anterior ultrastructure
Polymerase Chain Reaction
Progesterone blood
RNA, Messenger analysis
Receptors, Estradiol analysis
Receptors, Estradiol physiology
Receptors, LHRH analysis
Time Factors
Follicular Phase physiology
RNA, Messenger genetics
Receptors, LHRH genetics
Receptors, LHRH physiology
Sheep physiology
Subjects
Details
- Language :
- English
- ISSN :
- 0013-7227
- Volume :
- 135
- Issue :
- 4
- Database :
- MEDLINE
- Journal :
- Endocrinology
- Publication Type :
- Academic Journal
- Accession number :
- 7925096
- Full Text :
- https://doi.org/10.1210/endo.135.4.7925096