Pulsatile Administration of Gonadotropin-Releasing Hormone Agonist to Gilts Actively Immunized against Gonadotropin-Releasing Hormone

Abstract

Sexually mature gilts (n = 20) were actively immunized against GnRH. Primary and booster immunizations of GnRH conjugated to bovine serum albumin induced production of antibodies in all gilts. Nineteen of the gilts became acyclic with suppressed concentrations of gonadotropins and estradiol. Intravenous challenges with 100 micrograms GnRH and 5 micrograms D-(Ala6, des-Gly-NH2(10)) ethylamide GnRH (a GnRH agonist that did not cross-react with antibodies produced by the gilts) caused release of LH and FSH, indicating maintenance of secretory capacity of pituitary gonadotropes in the immunized animals. Gilts were given 100 ng GnRH agonist at 2-h intervals for 72 h (n = 4) or 144 h (n = 10) or did not receive agonist (n = 5). Blood samples were taken every 6 h, and detectable concentrations of LH were observed in 42% and 52% of samples taken from gilts treated with or without agonist. In contrast, serum concentrations of FSH and estradiol were undetectable. Reproductive tracts and anterior pituitaries were taken from gilts at the conclusion of pulsatile administration of GnRH agonist or at 144 h for controls. Pituitary concentration of LH and FSH, uterine wet and dry weight, and size of the uterus were similar among groups. Paired ovarian weights for treated gilts pulsed with GnRH agonist for 72 h were heavier (P less than .05); however, ovaries from all immunized gilts were atrophied without follicular structures.(ABSTRACT TRUNCATED AT 250 WORDS)

Impairment of follicular development by intra-ovarian infusion of gonadotrophin-releasing hormone antiserum in prepubertal pigs

“…These results are similar to those reported previously where ovaries taken from gilts actively immunized against GnRH contained few antral follicles and most (> 98%) of the follicles with >4 layers of granulosa cells were atretic (Esbenshade, 1987;Traywick & Esbenshade, 1988 (Aten et ai, 1986;Ireland et ai, 1988). Specific receptors that bind GnRH and GnRH agonist have also been shown to exist in a range of species (Clayton et ai, 1979;Jones et ai, 1980;Latouche et ai, 1989) and the actions of these compounds on the ovary have been reported to be both stimu¬ latory and inhibitory.…”

“…Ovarian and uterine weights in immunized animals were reduced, the ovaries contained few antral follicles, and a high percent¬ age of follicles with >4 layers of granulosa cells were atretic (Esbenshade, 1987; Traywick & Esbenshade, 1988). Several approaches, none of which has been successful, have been employed to induce follicular development in these acyclic pigs.…”

“…Gilts, actively immunized against GnRH, did not respond to a single injection or multiple injections of pregnant mares' serum gonadotrophin (PMSG) and intravenous injections of lyophilized pituitary extracts (Esbenshade, 1987). Attempts to induce follicular development were unsuccessful when a GnRH agonist, which did not cross react with the GnRH antibodies, was administered every other hour for 72 or 144 h (Traywick & Esbenshade, 1988).…”

Secretion of Gonadotropins and Estimated Releasable Pools of Gonadotropin-Releasing Hormone and Gonadotropins during Establishment of Suckling-Induced Inhibition of Gonadotropin Secretion in the Sow

“…Synthetic GnRH (acetate salt; Sigma) was radioiodinated by the iodogen method [22], and the labeled hormone was separated from free iodine by anionexchange chromatography [23]. The GnRH antiserum ESB-297 used in this assay was raised in our laboratory and has been validated [8,24,25]. The range of standards was 0.313 to 80 pg/tube with an average assay sensitivity of 4.9 pg/ ml at 95% binding.…”

Immunization of beef heifers against gonadotropin-releasing hormone prevents luteal activity and pregnancy: Effect of conjugation to different proteins and effectiveness of adjuvants1

“…Conjugation of GnRH to a carrier protein and emulsion with an adjuvant is neeessary to produce antibodies. Immunization of cattle against GnRH has been accomplished by conjugation of GnRH to a carrier protein (Johnson et al, 1988;Wettemann and Castrée, 1994;Prendiville et al, 1995) or by recombinant DNA techniques (van der Zee et al, 1995;Sosa et al, 2000;Hemandez et al, 2005). Booster immunizations increase antibody titers, and the number of boosters necessary to achieve adequate antibody titers may vary among individuals and species.…”