Centre of Reproductive Medicine and Andrology, University of Münster, Münster D-48149, Germany.
Asian J Androl. 2011 Jan;13(1):130-8. doi: 10.1038/aja.2010.97. Epub 2010 Nov 15.
The potential of spermatozoa to become motile during post-testicular maturation, and the relationship between the cytoplasmic droplet and fertilizing capacity are reviewed. Post-testicular maturation of spermatozoa involves the autonomous induction of motility, which can occur in vivo in testes with occluded excurrent ducts and in vitro in testicular explants, and artefactual changes in morphology that appear to occur in the testis in vitro. Both modifications may reflect time-dependent oxidation of disulphide bonds of head and tail proteins. Regulatory volume decrease (RVD), which counters sperm swelling at ejaculation, is discussed in relation to loss of cytoplasmic droplets and consequences for fertility. It is postulated that: (i) fertile males possess spermatozoa with sufficient osmolytes to drive RVD at ejaculation, permitting the droplet to round up and pinch off without membrane rupture; and (ii) infertile males possess spermatozoa with insufficient osmolytes so that RVD is inadequate, the droplet swells and the resulting flagellar angulation prevents droplet loss. Droplet retention at ejaculation is a harbinger of infertility caused by failure of the spermatozoon to negotiate the uterotubal junction or mucous and reach the egg. In this hypothesis, the epididymis regulates fertility indirectly by the extent of osmolyte provision to spermatozoa, which influences RVD and therefore droplet loss. Man is an exception, because ejaculated human spermatozoa retain their droplets. This may reflect their short midpiece, approximating head length, permitting a swollen droplet to extend along the entire midpiece; this not only obviates droplet migration and flagellar angulation but also hampers droplet loss.
本文回顾了精子在睾丸后成熟过程中获得运动能力的潜力，以及细胞质滴与受精能力之间的关系。精子的睾丸后成熟涉及自发诱导的运动能力，这种能力可以在阻塞输出管的睾丸中体内发生，也可以在睾丸外植体中体外发生，同时还伴随着体外睾丸中形态学的人为变化。这两种变化都可能反映了头部和尾部蛋白中二硫键的时间依赖性氧化。还讨论了与细胞质滴丢失和生育能力相关的调节体积减少（RVD），以对抗射精时精子肿胀。提出了以下假设：（i）有生育能力的男性拥有具有足够渗透物的精子，可以在射精时驱动 RVD，从而使细胞质滴变圆并脱落而不会破裂；（ii）无生育能力的男性拥有的精子渗透物不足，因此 RVD 不足，细胞质滴肿胀，导致鞭毛弯曲，阻止细胞质滴丢失。射精时细胞质滴的保留是精子不能通过输卵管连接或粘液并到达卵子而导致不育的先兆。在这个假设中，附睾通过向精子提供渗透物的程度间接调节生育能力，这影响了 RVD ，因此也影响了细胞质滴的丢失。人类是一个例外，因为射出的人类精子保留了它们的细胞质滴。这可能反映了它们的中段较短，接近头部长度，允许肿胀的细胞质滴沿整个中段延伸；这不仅避免了细胞质滴迁移和鞭毛弯曲，也阻止了细胞质滴丢失。
