Department of Applied Biology, University of Perugia, Perugia, Italy.
Theriogenology. 2012 Sep 1;78(4):715-23. doi: 10.1016/j.theriogenology.2012.02.012. Epub 2012 Jun 14.
There is increasing evidence that the particulate fraction of seminal plasma plays an important role in reproduction of several mammalian species. However, the origin and role of these granules in the physiology of rabbit spermatozoa is partially unknown. The aim of this study was to investigate the implication of prostate gland in the production and secretion of granules into the rabbit semen and the role of prostate-derived granules in the sperm acrosome reaction. Light and electron microscopy of the prostate gland showed that the anterior and middle tracts of the prostate (namely the proprostate and prostate, respectively) are chiefly implicated in the secretion of granules of different size: smaller granules (SG; 0.5 μm) and large granules (LG; 4 μm). Two major patterns of secretion were identified, based on electron microscope views: storage granules (large granules) seem to empty inner smaller granules directly into the duct by exocytosis, or the storage vesicle itself is released in toto into the ducts (diacytosis). In vitro experiments using granules from vasectomized rabbits, to exclude testicular origin of granules, showed that granules reduce the acrosome reaction of Percoll-selected spermatozoa, independently of the size. Interestingly, spermatozoa incubated with heat-treated granules showed a higher sperm acrosome reaction rate, suggesting a potential role of granule-derived proteins in this process. Inhibition of the acrosome reaction is a crucial event in rabbit reproduction; ejaculated spermatozoa have to wait for a long time (8-16 h) for egg availability in the female tract after mating. Taking together, our results demonstrate that prostate granules secreted either by exocytosis or diacytosis can preserve spermatozoa fertilizing ability, by preventing sperm acrosome reaction. The type of granule-derived proteins or other macromolecules implicated in this process should be further investigated.
越来越多的证据表明，精液的颗粒部分在几种哺乳动物的生殖中起着重要作用。然而，这些颗粒在兔精子生理学中的起源和作用尚不完全清楚。本研究旨在探讨前列腺在颗粒产生和分泌到兔精液中的作用，以及前列腺衍生颗粒在精子顶体反应中的作用。前列腺的光镜和电镜观察显示，前列腺的前、中区（即前前列腺和前列腺）主要参与不同大小颗粒的分泌：较小的颗粒（SG；0.5μm）和大颗粒（LG；4μm）。基于电镜观察，确定了两种主要的分泌模式：储存颗粒（大颗粒）似乎通过胞吐作用直接将较小的内部颗粒排入导管，或者储存囊泡本身整体释放到导管中（出胞作用）。使用来自输精管切除术兔的颗粒进行的体外实验，以排除颗粒的睾丸起源，表明颗粒减少了 Percoll 选择的精子的顶体反应，与颗粒大小无关。有趣的是，与热处理颗粒孵育的精子显示出更高的精子顶体反应率，这表明颗粒衍生蛋白在这个过程中可能发挥作用。顶体反应的抑制是兔生殖中的一个关键事件；在交配后，精子在雌性生殖道中等待卵子出现的时间很长（8-16 小时）。综上所述，我们的结果表明，前列腺颗粒通过胞吐作用或出胞作用分泌，可以通过防止精子顶体反应来维持精子的受精能力。在这个过程中涉及的颗粒衍生蛋白或其他大分子的类型应进一步研究。
