Wheaton J E, Godfrey R W
Department of Animal Science, University of Minnesota, St. Paul, MN 55108, USA.
Theriogenology. 2003 Sep 15;60(5):933-41. doi: 10.1016/s0093-691x(03)00104-3.
Active immunization against inhibin has been shown to advance puberty and increase ovulation rate in ewe lambs; but in ram lambs, effects on puberty and sperm production are equivocal. The objective of the present study was to determine whether active immunization against an inhibin alpha-subunit peptide advances the onset of puberty in ram lambs. St. Croix hair sheep ram lambs were assigned to inhibin-immunized (n = 7) and control (n = 8) treatment groups. Lambs in the inhibin-immunized group were immunized against a synthetic peptide-carrier protein conjugate, alpha-(1-25)-human alpha-globulin (halpha-G), and control lambs were immunized against halpha-G. Lambs were immunized at 3, 7, 13, 19, 25, 31, and 37 weeks of age. On the day of immunization a blood sample was collected and lambs were weighed. Another blood sample was collected 1 week following each immunization. At 20 weeks of age additional blood samples were collected at 20 min intervals for 8h. Beginning at 20 weeks of age and at weekly intervals thereafter, scrotal circumference (SC) was measured and semen was collected using electroejaculation. A subsequent ejaculate was collected 1 week following onset of puberty, which was defined as the week of age when an ejaculate first contained > or =50 x 10(6) sperm cells. In control lambs, plasma alpha-(1-25)-antibody (Ab) was nondetectable. In inhibin-immunized lambs, alpha-(1-25)-Ab titer increased from 7 to 25 weeks of age and then plateaued at a level that varied (P<0.001) among animals. Body weight and SC of control and inhibin-immunized lambs were similar at the onset of puberty. At pubertal onset inhibin-immunized lambs were older than control lambs (31.9+/-0.5 vs. 29.5+/-0.7 weeks of age, P<0.05). Plasma FSH concentrations were similar in control and inhibin-immunized lambs from 3 to 38 weeks of age. Plasma LH levels were lower (P<0.01) in inhibin-immunized than control lambs. During the 8-h blood sampling period at 20 weeks of age, LH and testosterone concentrations were lower (P<0.05) in inhibin-immunized than control ram lambs, and the LH pulse frequency was similar in the two groups of animals. The decreased LH secretion is consistent with the immunoneutralization of a putative inhibin alpha-subunit-related peptide that stimulates LH secretion in ram lambs. Present findings show that active immunization against an inhibin alpha-peptide delays rather than advances puberty in ram lambs.
已证明，对抑制素进行主动免疫可使母羊羔羊青春期提前并提高排卵率；但对公羊羔羊而言，对青春期和精子生成的影响并不明确。本研究的目的是确定对抑制素α亚基肽进行主动免疫是否能使公羊羔羊青春期提前。将圣克罗伊毛用绵羊公羊羔羊分为抑制素免疫组（n = 7）和对照组（n = 8）。抑制素免疫组的羔羊针对合成肽 - 载体蛋白偶联物α-(1 - 25)-人α球蛋白（halpha - G）进行免疫，对照组羔羊则针对halpha - G进行免疫。羔羊在3、7、13、19、25、31和37周龄时进行免疫。在免疫当天采集血样并对羔羊称重。每次免疫后1周再采集一次血样。在20周龄时，每隔20分钟采集一次血样，共采集8小时。从20周龄开始及之后每周，测量阴囊周长（SC）并用电刺激采精。在青春期开始后1周采集后续精液样本，青春期定义为精液首次含有≥50×10⁶个精子细胞的周龄。在对照组羔羊中，血浆α-(1 - 25)-抗体（Ab）检测不到。在抑制素免疫的羔羊中，α-(1 - 25)-Ab滴度从7周龄至25周龄升高，然后在不同动物间达到一个稳定水平（P<0.001）。在青春期开始时，对照组和抑制素免疫组羔羊的体重和SC相似。在青春期开始时，抑制素免疫的羔羊比对照组羔羊年龄大（31.9±0.5岁对29.5±0.7岁，P<0.05）。在3至38周龄期间，对照组和抑制素免疫组羔羊的血浆促卵泡激素（FSH）浓度相似。抑制素免疫组羔羊的血浆促黄体生成素（LH）水平低于对照组（P<0.01）。在20周龄的8小时血样采集期间，抑制素免疫的公羊羔羊的LH和睾酮浓度低于对照组（P<0.05），两组动物的LH脉冲频率相似。LH分泌减少与推测的抑制素α亚基相关肽被免疫中和一致，该肽可刺激公羊羔羊LH分泌。目前的研究结果表明，对抑制素α肽进行主动免疫会延迟而非提前公羊羔羊的青春期。
