Weil S, Rozenboim I, Degen A A, Dawson A, Friedländer M, Rosenstrauch A
Jacob Blaustein Institute for Desert Research, Ben-Gurion University of the Negev, Beer Sheva, 84105, Israel.
Gen Comp Endocrinol. 1999 Jul;115(1):23-8. doi: 10.1006/gcen.1999.7276.
The relationships between testicular and plasma hormone levels and the decline in fertility in aging roosters were examined. Body mass, testicular mass, and fertility were measured in roosters from 20 to 72 weeks of age. Plasma was assayed for LH and testosterone, and estradiol and testicular extracts were assayed for testosterone and estradiol contents. Fertility increased rapidly in young roosters to a peak of 96.2 +/- 3.9% at 37 weeks of age. Thereafter, fertility declined and by 72 weeks of age was significantly lower than at 37 weeks. Plasma LH reached 16.8 +/- 2.5 ng/ml at 27 weeks and remained high until 60 weeks of age, when it decreased significantly. Plasma and testicular testosterone levels increased from low levels in young birds to a peak that coincided with highest fertility and declined thereafter. Plasma and testicular estradiol showed a striking inverse relationship with testosterone. Plasma estradiol was 29.4 +/- 4.0 pg/ml in 20-week-old birds, decreased rapidly as testosterone increased, and increased again in older birds as testosterone decreased. Thus, the decline in fertility in aging roosters was associated with a decrease in plasma LH and testosterone and an increase in plasma and testicular estradiol. It is suggested that plasma levels of LH and testosterone in roosters are regulated by a negative feedback mechanism involving estradiol that is produced not only by the aromatization of testosterone in the brain but also by peripheral estradiol originating in the testes and that estradiol has a major role in the decline in fertility in aging roosters.
研究了老龄公鸡睾丸激素和血浆激素水平与生育力下降之间的关系。测定了20至72周龄公鸡的体重、睾丸重量和生育力。检测血浆中的促黄体生成素（LH）和睾酮，以及睾丸提取物中的睾酮和雌二醇含量。年轻公鸡的生育力迅速上升，在37周龄时达到峰值96.2±3.9%。此后，生育力下降，到72周龄时显著低于37周龄时。血浆LH在27周龄时达到16.8±2.5 ng/ml，并一直保持在较高水平，直到60周龄时显著下降。血浆和睾丸中的睾酮水平从幼鸟时的低水平上升到与最高生育力同时出现的峰值，此后下降。血浆和睾丸中的雌二醇与睾酮呈现出显著的负相关关系。20周龄鸟类的血浆雌二醇为29.4±4.0 pg/ml，随着睾酮水平的升高而迅速下降，在老龄鸟类中随着睾酮水平的下降又再次升高。因此，老龄公鸡生育力的下降与血浆LH和睾酮的减少以及血浆和睾丸中雌二醇的增加有关。研究表明，公鸡血浆中LH和睾酮的水平受一种负反馈机制调节，该机制涉及不仅由大脑中睾酮芳香化产生的雌二醇，还包括睾丸来源的外周雌二醇，并且雌二醇在老龄公鸡生育力下降中起主要作用。
