Concentration of gonadotropin-releasing hormone receptor messenger ribonucleic acid in pituitary tissue of orchidectomized sheep: effect of passive immunization against gonadotropin-releasing hormone.
The effect of immunoneutralization of gonadotropin-releasing hormone (GnRH) on LH secretion and concentrations of GnRH receptor, GnRH receptor mRNA, and gonadotropin subunit mRNA in pituitary tissue of orchidectomized sheep (wethers) was assessed. Thirty-six wethers were assigned at random to one of six treatment groups (six wethers per group). Thirty wethers (groups 2 to 6) received 200 ml, (i.v.) of anti-GnRH antisera at passive immunization (PI). Anterior pituitary tissue was collected .5, 1, 2, 4, or 8 d after PI from wethers in groups 2 to 6, respectively. Pituitary tissue was also collected from unimmunized wethers (Group 1). Intravenous administration of anti-GnRH sera increased anti-GnRH activity to 69.1 +/- 7% (percentage of total 125I-labeled GnRH bound by a 1:1,000 serum:GEL-PBS dilution) within 1 h of PI. Anti-GnRH activity declined gradually during the period after PI, and 8 d after PI anti-GnRH activity was 57.2 +/- 1.7%. Serum concentration of LH was significantly reduced, relative to the pretreatment (16.1 +/- 1.8 ng/mL) level, within 4 h (7.6 +/- 1.5 ng/mL) of PI, and the LH level was 10% of the pretreatment concentration 8 d after PI (1.6 +/- 0.2 ng/mL). Steady-state concentration of GnRH receptor mRNA decreased progressively during the period after PI and was significantly reduced, relative to the level in unimmunized control wethers (.44 +/- .03 pg/micron total RNA) d after PI. Tissue concentrations of GnRH receptor and mRNA for the alpha, LH alpha, and FISH beta subunits were also reduced (P < .05) by PI. These data indicate that maintenance of steady-state concentrations of GnRH receptor and GnRH receptor mRNA requires continued GnRH stimulation.
Sakurai
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Department of Animal Science, University of California, Davis 95616, USA.
Adams
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BM
Adams
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D000818:Animals; D005640:Follicle Stimulating Hormone / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D007987:Gonadotropin-Releasing Hormone / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism; D007106:Immune Sera / Q000276:immunology / Q000494:pharmacology; D007116:Immunization, Passive / Q000379:methods / Q000662:veterinary*; D007986:Luteinizing Hormone / Q000032:analysis / Q000097:blood / Q000235:genetics; D008297:Male; D009919:Orchiectomy / Q000662:veterinary*; D010903:Pituitary Gland, Anterior / Q000737:chemistry* / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis* / Q000378:metabolism; D011897:Random Allocation; D011966:Receptors, LHRH / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D012756:Sheep / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D013997:Time Factors
D007106:Immune Sera; D012333:RNA, Messenger; D011966:Receptors, LHRH; D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone