title: Responses of ram lambs to active immunization against testosterone and luteinizing hormone-releasing hormone.
abstract: Active immunization of young ram lambs against testosterone and luteinizing hormone-releasing hormone (LHRH) was shown to block the growth attributes characteristic of intact ram lambs. Testosterone and LHRH-immunized lambs grew at a slower rate and converted feed to live weight gain less efficiently than albumin-immunized controls. Lambs immunized against testosterone and LHRH had high antibody titers for their respective antigens. Moreover, testosterone-immunized lambs had high serum concentrations of luteinizing hormone (LH) and testosterone, whereas LHRH-immunized lambs had low to nondetectable serum concentrations of these hormones. Release of LH and testosterone following the intravenous administration of LHRH (250 ng) was absent in LHRH-immunized lambs, but quantitatively similar for intact and albumin-immunized control lambs. Testosterone-immunized lambs responded as did conventional castrates with a large LH release, but testosterone concentrations were unchanged. These findings are discussed relative to the integrity of the hypothalamic-pituitary-testicular endocrine axis and the importance of gonadotropin support for normal testicular development. These data show that LHRH immunoneutralization effectively retards testicular development and produces a castration effect in young ram lambs.
mesh_terms: D000818:Animals; D001835:Body Weight; D002369:Castration / Q000379:methods; D007987:Gonadotropin-Releasing Hormone; D007114:Immunization; D008297:Male; D012756:Sheep / Q000254:growth & development* / Q000502:physiology; D013737:Testis / Q000254:growth & development* / Q000502:physiology; D013739:Testosterone / Q000276:immunology*
chemical_list: D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone