Rosati Luigi, Falvo Sara, Chieffi Baccari Gabriella, Santillo Alessandra, Di Fiore Maria Maddalena
Dipartimento di Biologia, Università degli Studi di Napoli "Federico II", 80100 Napoli, Italy.
Dipartimento di Scienze e Tecnologie Ambientali, Biologiche e Farmaceutiche, Università degli Studi della Campania "Luigi Vanvitelli", 81100 Caserta, Italy.
Animals (Basel). 2021 Jun 12;11(6):1763. doi: 10.3390/ani11061763.
Estrogens are important physiological regulators of testicular activity in vertebrates. Estrogen levels depend on the activity of P450 aromatase, the enzyme responsible for the irreversible conversion of testosterone into 17β-estradiol. Therefore, P450 aromatase is the key player in the aromatase-estrogen system. The present review offers a comparative overview of P450 aromatase activity in male gonads of amphibians, reptiles, and birds, with a particular emphasis on the functions of the aromatase-estrogen system in these organisms during their developmental and adult stages. The aromatase-estrogen system appears to be crucial for the sex differentiation of gonads in vertebrates. Administration of aromatase inhibitors prior to sexual differentiation of gonads results in the development of males rather than females. In adults, both aromatase and estrogen receptors are expressed in somatic cells, Leydig and Sertoli cells, as well as germ cells, with certain differences among different species. In seasonal breeding species, the aromatase-estrogen system serves as an "on/off" switch for spermatogenesis. In some amphibian and reptilian species, increased estrogen levels in post-reproductive testes are responsible for blocking spermatogenesis, whereas, in some species of birds, estrogens function synergistically with testosterone to promote spermatogenesis. Recent evidence indicates that the production of the aromatase enzyme in excessive amounts reduces the reproductive performance in avian species of commercial interest. The use of aromatase inhibitors to improve fertility has yielded suitable positive results. Therefore, it appears that the role of the aromatase-estrogen system in regulating the testicular activity differs not only among the different classes of vertebrates but also among different species within the same class.
雌激素是脊椎动物睾丸活动的重要生理调节因子。雌激素水平取决于P450芳香化酶的活性，该酶负责将睾酮不可逆地转化为17β-雌二醇。因此，P450芳香化酶是芳香化酶-雌激素系统的关键参与者。本综述对两栖动物、爬行动物和鸟类雄性性腺中P450芳香化酶的活性进行了比较概述，特别强调了芳香化酶-雌激素系统在这些生物体发育和成年阶段的功能。芳香化酶-雌激素系统似乎对脊椎动物性腺的性别分化至关重要。在性腺性别分化之前给予芳香化酶抑制剂会导致雄性而非雌性的发育。在成年动物中，芳香化酶和雌激素受体在体细胞、睾丸间质细胞和支持细胞以及生殖细胞中均有表达，不同物种之间存在一定差异。在季节性繁殖物种中，芳香化酶-雌激素系统充当精子发生的“开/关”开关。在一些两栖动物和爬行动物物种中，生殖后睾丸中雌激素水平的升高导致精子发生受阻，而在一些鸟类物种中，雌激素与睾酮协同作用以促进精子发生。最近的证据表明，过量产生芳香化酶会降低具有商业价值的鸟类物种的繁殖性能。使用芳香化酶抑制剂来提高生育能力已取得了合适的积极成果。因此，芳香化酶-雌激素系统在调节睾丸活动中的作用似乎不仅在不同类别的脊椎动物之间存在差异，而且在同一类别的不同物种之间也存在差异。
