Kirby J D, Mankar M V, Hardesty D, Kreider D L
Department of Poultry Science, University of Arkansas, Fayetteville 72701, USA.
Biol Reprod. 1996 Oct;55(4):910-6. doi: 10.1095/biolreprod55.4.910.
It has been well established that thyroid hormones play an important role in regulating the onset of puberty and reproductive function in birds. In mammals it has been shown that transient hypothyroidism induced with the reversible goitrogen 6-N-propyl-2-thiouracil (PTU) can result in tremendous increases in testis size and sperm production and that the timing of hypothyroidism must correspond to the period of Sertoli cell proliferation. As the period of Sertoli cell proliferation is not precisely known in the fowl, an experiment was conducted to determine whether chicken testes have a similar window of sensitivity to PTU treatment. Broiler breeder male chicks (Peterson) were placed in floor pens at one day of age and reared according to the breeder's management guide for the entire 28-wk duration (controls) or up to the point of dietary treatment with PTU (0.1% w:w) for 6 wk that began at 2-wk intervals (2-8, 4-10, 6-12, 8-14, and 10-16 wk of age); after treatment, birds were returned to feed restriction and photostimulated at 20 wk of age. Birds were bled and killed, and testes were collected at 4-wk intervals. At 28 wk, one testis was fixed for histological examination and one was immediately placed in liquid N2 for sperm counts. Treatment with PTU from 6 to 12 wk of age resulted in a 96% increase in mean testis weight at 28 wk of age (treated 39.3 +/- 4.1 g per testis vs. control 20.0 +/- 1.6 g per testis). These testes exhibited normal morphology and increased relative sperm production. Treatment with PTU from either 8 to 14 or 10 to 16 wk of age resulted in approximately a 35% increase in testis mass at 28 wk of age relative to the control value (27.2 +/- 2.0 g and 27.7 +/- 3.6 g vs. 20.0 +/- 1.6 g per testis, respectively). However, both of these groups clearly demonstrated precocious puberty and abnormal spermatogenesis. These results suggest that appropriately timed PTU treatment may result in permanent increases in testis size and sperm production in the domestic fowl.
甲状腺激素在调节鸟类青春期的开始和生殖功能方面起着重要作用，这一点已经得到充分证实。在哺乳动物中，研究表明，用可逆性甲状腺肿形成剂6 - N - 丙基 - 2 - 硫氧嘧啶（PTU）诱导的短暂性甲状腺功能减退会导致睾丸大小和精子生成大幅增加，而且甲状腺功能减退的时间必须与支持细胞增殖期相对应。由于家禽中支持细胞增殖期的确切时间尚不清楚，因此进行了一项实验，以确定鸡睾丸对PTU处理是否有类似的敏感窗口期。肉种鸡雄性雏鸡（彼得森品种）在1日龄时放入地面饲养栏，并按照饲养者的管理指南饲养整个28周（对照组），或者在2周龄开始每隔2周用PTU（0.1%重量比）进行6周的饮食处理（处理组分别为2 - 8周龄、4 - 10周龄、6 - 12周龄、8 - 14周龄和10 - 16周龄）；处理后，鸡只恢复限饲，并在20周龄时进行光照刺激。每隔4周对鸡只进行采血和宰杀，并收集睾丸。在28周龄时，一个睾丸固定用于组织学检查，另一个立即放入液氮中进行精子计数。6至12周龄用PTU处理，在28周龄时平均睾丸重量增加了96%（处理组每个睾丸39.3±4.1克，对照组每个睾丸20.0±1.6克）。这些睾丸形态正常，相对精子生成增加。8至14周龄或10至16周龄用PTU处理，在28周龄时睾丸质量相对于对照组增加了约35%（分别为27.2±2.0克和27.7±3.6克，对照组每个睾丸20.0±1.6克）。然而，这两组均明显表现出性早熟和异常精子发生。这些结果表明，适时的PTU处理可能会使家鸡的睾丸大小和精子生成永久性增加。
