title: The effect of early postnatal treatment with a gonadotropin-releasing hormone agonist on the developmental profiles of testicular steroid hormones in the intact male pig.
abstract: Three studies examined the effects of early postnatal treatment with a GnRH agonist on plasma concentrations of testosterone, dehydroepian-drosterone sulfate, 16-androstene steroids in fat and salivary glands, androstenone in fat and plasma, and testicular development of intact male pigs. The first study involved 45 7-d-old pigs assigned to three treatment groups: 1) boars administered 100 microg/kg of Lupron depot, 2) boars administered 200 microg/kg of Lupron depot, and 3) control boars receiving a saline carrier. The second study involved 20 7-d-old pigs assigned to two treatments: daily injection of 200 microL of 0.5 mg/mL Lupron from d 7 to 35 and controls treated with saline. The third study involved a total of 100 animals assigned to 10 groups of 10 based on their age at slaughter. These groups were subdivided into one of two treatments: 1) boars injected with 200 microL of 0.5 mg/mL of Lupron from d 3 to 35 and 2) control boars injected with saline. Testicular steroid hormone concentrations in plasma decreased (P < 0.01) within 7 d of GnRH agonist treatment. Following cessation of treatment, steroid levels increased to control levels and remained constant until the final rise at 5 mo. Plasma testosterone levels in the 100 microg/kg depot treatment group were higher (P < 0.05) than that of the 200 microg/kg and control group at 164 d of age. There were no differences between treatments (P > 0.05) in testicular steroid hormone levels at the end of study 2 or 3. There were no differences (P > 0.05) in concentrations of 16-androstene steroids in salivary glands between any of the treatment groups at market weight in studies 1 and 2. Fat androstenone levels measured in the third study ranged between 0.6 microg/g and 4.2 microg/g at 7 to 28 d of age. Treatment with GnRH agonist decreased plasma steroid levels and testicular development; however, by d 60 testicular size and weight were at control levels and remained similar until 180 d of age. The results of these studies indicate that daily administration of a GnRH agonist significantly decreased testicular development and steroidogenesis only during treatment, but testis growth and steroidogenesis had returned to control levels by 60 d of age in male pigs. Suppression of the early postnatal rise in testicular steroid hormones did not affect growth performance or steroid hormone levels at 5 to 6 mo of age.
authors.affiliation: Department of Animal and Poultry Science, University of Guelph, Ontario, Canada.
authors.forename: P A
authors.initials: PA
authors.lastname: Sinclair
authors.forename: E J
authors.initials: EJ
authors.lastname: Squires
authors.forename: J I
authors.initials: JI
authors.lastname: Raeside
authors.forename: J H
authors.initials: JH
authors.lastname: Britt
authors.forename: V G
authors.initials: VG
authors.lastname: Hedgpeth
mesh_terms: D000273:Adipose Tissue / Q000737:chemistry; D000736:Androstenes / Q000032:analysis; D000818:Animals; D019314:Dehydroepiandrosterone Sulfate / Q000032:analysis; D016729:Leuprolide / Q000494:pharmacology*; D008297:Male; D009929:Organ Size / Q000187:drug effects; D011897:Random Allocation; D013363:Submandibular Gland / Q000737:chemistry; D013552:Swine / Q000254:growth & development*; D013737:Testis / Q000254:growth & development* / Q000378:metabolism; D013739:Testosterone / Q000097:blood
chemical_list: D000736:Androstenes; D013739:Testosterone; D019314:Dehydroepiandrosterone Sulfate; D016729:Leuprolide