Aspden W J, Rao A, Scott P T, Clarke I J, Trigg T E, Walsh J, D'Occhio M J
CSIRO Division of Tropical Animal Production, Tropical Beef Centre, Rockhampton, Queensland, Australia.
Biol Reprod. 1996 Aug;55(2):386-92. doi: 10.1095/biolreprod55.2.386.
The objective in this study was to characterize direct effects of the LHRH agonist, deslorelin, on anterior pituitary gland function in male cattle in the absence of gonadal feedback. Castrated bulls (steers), 30 mo old, were allocated to four groups: group 1, control, no treatment (n = 8); group 2, five deslorelin implants (approximately 250 micrograms total deslorelin/day) for 42 days (n = 8); group 3, control+ LHRH (50 micrograms i.m.) at weekly intervals (n = 3); group 4, five deslorelin implants+LHRH as for group 3 (n = 3). Plasma LH was similar (p > 0.05) for steers in groups 1 and 2 on Day 0 and lower (p < 0.05) for steers in group 2 on Day 4, and continued to decrease to Day 41 (group 1, 1.71 +/- 0.20 ng/ml [mean +/- SEM]; group 2, 0.38 +/- 0.03 ng/ml [p < 0.001]). Mean plasma concentrations of FSH were similar (p > 0.05) for steers in groups 1 and 2 on Day 0 and lower (p < 0.05) for steers in group 2 on Day 7, and declined to Day 41 (group 1, 43.5 +/- 3.9 ng/ml; group 2, 17.5 +/- 1.5 ng/ml [p < 0.001]). Steers in group 3 showed increases in plasma LH after injection of LHRH on all occasions, while steers in group 4 did not show increases in plasma LH from Day 14 onward. Mean relative pituitary contents (arbitrary units) of LH beta- and FSH beta-subunit mRNAs were reduced on Day 42 in steers treated with deslorelin (LH beta: groups 1 and 3, 1.56 +/- 0.27; groups 2 and 4, 0.08 +/- 0.01 [p < 0.001]; FSH beta: groups 1 and 3, 1.01 +/- 0.08; groups 2 and 4, 0.34 +/- 0.07 [p < 0.001]). However, alpha-subunit mRNA was similar for control steers and steers treated with deslorelin (groups 1 and 3, 1.00 +/- 0.11; groups 2 and 4, 0.86 +/- 0.12 [p > 0.1]). Pituitary content of LH, but not FSH, was reduced in steers treated with deslorelin. In summary, steers treated with deslorelin showed desensitization to natural LHRH, and this was associated with reduced pituitary contents of LH and FSH beta-subunit mRNAs, a reduction in pituitary content of LH, and decreases in plasma concentrations of LH and FSH. This demonstrated, for the first time, a direct action of LHRH agonist on LH and FSH beta-subunit gene expression in cattle, independent of gonadal feedback. Also, there was a differential effect of treatment with deslorelin on gonadotropin alpha- and beta-subunit mRNA contents in the anterior pituitary.
本研究的目的是在不存在性腺反馈的情况下，表征促黄体生成素释放激素（LHRH）激动剂地洛瑞林对雄性牛垂体前叶功能的直接影响。30月龄的去势公牛（阉牛）被分为四组：第1组为对照组，不进行处理（n = 8）；第2组，植入5个地洛瑞林植入物（地洛瑞林总量约250微克/天），持续42天（n = 8）；第3组，对照组 + 每周一次肌肉注射LHRH（50微克）（n = 3）；第4组，5个地洛瑞林植入物 + 与第3组相同的LHRH注射方案（n = 3）。第1组和第2组的阉牛在第0天的血浆促黄体生成素（LH）水平相似（p > 0.05），第2组的阉牛在第4天LH水平较低（p < 0.05），并持续下降至第41天（第1组，1.71 ± 0.20纳克/毫升[平均值 ± 标准误]；第2组，0.38 ± 0.03纳克/毫升[p < 0.001]）。第1组和第2组的阉牛在第0天的促卵泡生成素（FSH）平均血浆浓度相似（p > 0.05），第2组的阉牛在第7天FSH水平较低（p < 0.05），并下降至第41天（第1组，43.5 ± 3.9纳克/毫升；第2组，17.5 ± 1.5纳克/毫升[p < 0.001]）。第3组的阉牛在每次注射LHRH后血浆LH均升高，而第4组的阉牛从第14天起血浆LH未升高。在第42天，接受地洛瑞林治疗的阉牛垂体中LHβ和FSHβ亚基mRNA的平均相对含量（任意单位）降低（LHβ：第1组和第3组，1.56 ± 0.27；第2组和第4组，0.08 ± 0.01[p < 0.001]；FSHβ：第1组和第3组，1.01 ± 0.08；第2组和第4组，0.34 ± 0.07[p < 0.001]）。然而，对照组阉牛和接受地洛瑞林治疗的阉牛的α亚基mRNA相似（第1组和第3组，1.00 ± 0.11；第2组和第4组，0.86 ± 0.12[p > 0.1]）。接受地洛瑞林治疗的阉牛垂体中LH含量降低，但FSH含量未降低。总之，接受地洛瑞林治疗的阉牛对天然LHRH脱敏，这与垂体中LH和FSHβ亚基mRNA含量降低、垂体中LH含量减少以及血浆中LH和FSH浓度降低有关。这首次证明了LHRH激动剂对牛LH和FSHβ亚基基因表达有直接作用，且独立于性腺反馈。此外，地洛瑞林治疗对垂体前叶促性腺激素α和β亚基mRNA含量有不同影响。
