Miura T, Yamauchi K, Takahashi H, Nagahama Y
Department of Developmental Biology, National Institute for Basic Biology, Okazaki, Japan.
Proc Natl Acad Sci U S A. 1991 Jul 1;88(13):5774-8. doi: 10.1073/pnas.88.13.5774.
The importance of gonadotropins and androgens for spermatogenesis is generally accepted in vertebrates, but the role played by specific hormones has not been clarified. Under cultivation conditions, male Japanese eels (Anguilla japonica) have immature testes containing only premitotic spermatogonia, type A and early-type B spermatogonia. In the present study, a recently developed organ-culture system for eel testes was used to determine in vitro effects of various steroid hormones on spermatogenesis. After 9 days of culture in serum-free, chemically defined medium containing 11-ketotestosterone (10 ng/ml), a major androgen in male eels, type A and early-type B spermatogonia began mitosis, producing late-type B spermatogonia. After 18 days, zygotene spermatocytes with synaptonemal complexes appeared, indicating that meiosis had already started by this time. In testis fragments cultured for 21 days, round spermatids and spermatozoa were observed with spermatogenic cells at all stages of development. Addition of 11-ketotestosterone to the culture medium also caused a marked cytological activation of Sertoli cells. No other steroid hormones tested had such stimulatory effects. These results, together with our earlier observations, suggest the following sequence for the hormonal induction of spermatogenesis in eel testes; gonadotropin stimulates the Leydig cells to produce 11-ketotestosterone, which, in turn, activates the Sertoli cells leading to the completion of spermatogenesis. This is, thus, an example of an animal system in which all stages of spermatogenesis have been induced by hormonal manipulation in vitro.
促性腺激素和雄激素对脊椎动物精子发生的重要性已得到普遍认可，但特定激素所起的作用尚未明确。在养殖条件下，雄性日本鳗鲡（Anguilla japonica）的睾丸不成熟，仅含有有丝分裂前期精原细胞、A型和早期B型精原细胞。在本研究中，利用最近开发的鳗鲡睾丸器官培养系统来确定各种类固醇激素对精子发生的体外影响。在含有11-酮睾酮（10 ng/ml）（雄性鳗鲡的主要雄激素）的无血清化学限定培养基中培养9天后，A型和早期B型精原细胞开始有丝分裂，产生晚期B型精原细胞。18天后，出现了带有联会复合体的偶线期精母细胞，表明此时减数分裂已经开始。在培养21天的睾丸片段中，观察到了圆形精子细胞和精子，以及处于发育各阶段的生精细胞。向培养基中添加11-酮睾酮还导致支持细胞出现明显的细胞学激活。所测试的其他类固醇激素均无此类刺激作用。这些结果与我们早期的观察结果一起，提示了鳗鲡睾丸精子发生激素诱导的以下顺序：促性腺激素刺激睾丸间质细胞产生11-酮睾酮，而11-酮睾酮反过来激活支持细胞，从而导致精子发生的完成。因此，这是一个通过体外激素操作诱导精子发生所有阶段的动物系统实例。
