Tähkä K M, Teräväinen T, Pankakoski E, Jalkanen M
Division of Physiology, University of Helsinki, Finland.
Gen Comp Endocrinol. 1989 Nov;76(2):301-9. doi: 10.1016/0016-6480(89)90162-7.
Seasonal changes in testicular histology and steroidogenesis were investigated in the mole (Talpa europaea). Androgen synthesis was examined by incubating [4-14C]pregnenolone (P) and [4-14C]dehydroepiandrosterone (DHA) with testicular minces in a static incubation system. The metabolites formed were characterized by thin-layer chromatography. Morphological changes were studied by routine histological methods. During sexual quiescence spermatogenesis was arrested. The regressive seminiferous tubules consisted predominantly of Sertoli cells and spermatogonia. On the other hand, histological quantification suggested that season has no significant effects on the number or the nuclear dimensions of Leydig cells in this species. The capacity of the regressive testes (per unit weight) to metabolize P and DHA to testosterone (T) was somewhat greater in regressive (48.5%, 49.4%) than in active (33.2%, 41.6%) testes. The results also suggest that the greater in vitro T production encountered during reproductive quiescence is due possibly to an increase in the activity of 17 beta-hydroxysteroid dehydrogenase (per unit weight). Our data on Leydig cell numbers indicate, however, that the capacity of the individual Leydig cells to produce T is decreased during sexual regression. T. europaea appears to be quite exceptional among seasonally breeding small mammals exhibiting pronounced annual changes in spermatogenesis in that the testes retain a considerable enzymatic capacity to produce testosterone from pregnanes during sexual quiescence. The results suggest that pituitary as well as paracrine regulation of the annual testicular cycle in this species differs from that generally encountered in seasonal breeders.
对欧洲鼹鼠（Talpa europaea）睾丸组织学和类固醇生成的季节性变化进行了研究。在静态孵育系统中，通过将[4-¹⁴C]孕烯醇酮（P）和[4-¹⁴C]脱氢表雄酮（DHA）与睾丸碎块一起孵育来检测雄激素合成。通过薄层色谱法对形成的代谢产物进行表征。通过常规组织学方法研究形态学变化。在性静止期，精子发生停止。退化的生精小管主要由支持细胞和精原细胞组成。另一方面，组织学定量分析表明，季节对该物种睾丸间质细胞的数量或核尺寸没有显著影响。退化睾丸（每单位重量）将P和DHA代谢为睾酮（T）的能力在退化睾丸中（48.5%，49.4%）比在活跃睾丸中（33.2%，41.6%）略高。结果还表明生殖静止期体外T产量较高可能是由于17β-羟基类固醇脱氢酶（每单位重量）活性增加所致。然而，我们关于睾丸间质细胞数量的数据表明，在性退化期间单个睾丸间质细胞产生T的能力下降。欧洲鼹鼠在季节性繁殖的小型哺乳动物中似乎相当特殊，其精子发生呈现明显的年度变化，即睾丸在性静止期仍保留相当大的从孕烷生成睾酮的酶促能力。结果表明，该物种垂体以及旁分泌对年度睾丸周期的调节与季节性繁殖动物中通常遇到的情况不同。
