Dipartimento di Biologia Strutturale e Funzionale, Università di Napoli Federico II, Complesso Universitario di Monte S. Angelo, Naples, Italy.
Theriogenology. 2010 May;73(8):1037-43. doi: 10.1016/j.theriogenology.2009.11.030. Epub 2010 Feb 2.
In Bos taurus, at ejaculation, epididymal sperm acquire a number of proteins secreted in the seminal plasma that increase their ability to interact with the female reproductive tract. Sperm-oviduct interaction comprises a transient sperm adhesion to the isthmus, the lower portion of the oviduct, followed by sperm release around ovulation. Oviductal fluid molecules, such as sulfated glycoconjugates and disulfide-reductants, are able to release bovine ejaculated sperm bound to the oviductal epithelium in vitro through the reduction of sperm surface protein disulfides to sulfhydryls. To understand whether the sperm molecules sensitive to releasing signals are already exposed on the surface of epididymal sperm, we studied the ability of cauda epididymal sperm to adhere to the oviductal epithelium and to be released by sulfated glycoconjugates and the disulfide-reductant penicillamine. Surface protein sulfhydryls in cauda epididymal sperm were analyzed in the initial suspension, in sperm bound to the in vitro-cultured oviductal epithelium, and in released sperm. Results showed that epididymal sperm are able to bind the oviductal epithelium in vitro, although at a lower extent than frozen-thawed ejaculated sperm; the interaction is mediated by oviductal cell microvilli that closely bind to the plasma membrane of the sperm head rostral region, as previously shown for ejaculated sperm. The sulfated glycoconjugates heparin, fucoidan, and dextran sulfate, as well as the disulfide-reductant penicillamine, are all powerful inducers of sperm release. The level of sulfhydryls in sperm surface proteins was (1) high in the initial sperm suspension; (2) low in bound sperm; (3) markedly increased in sperm released by heparin or by penicillamine. In conclusion, epididymal sperm are already able to bind the oviductal epithelium and to respond to the inducers of release through the reduction of sperm surface protein disulfides to sulfhydryls.
在牛中，在射精时，附睾精子获得许多在精液中分泌的蛋白质，这些蛋白质增加了它们与雌性生殖道相互作用的能力。精子-输卵管相互作用包括精子短暂地附着在输卵管的峡部（输卵管的下部），然后在排卵时释放精子。输卵管液分子，如硫酸化糖缀合物和二硫键还原剂，能够通过将精子表面蛋白二硫键还原为巯基，体外释放与输卵管上皮结合的牛射出的精子。为了了解对释放信号敏感的精子分子是否已经暴露在附睾精子的表面，我们研究了尾部附睾精子附着在输卵管上皮上的能力，以及硫酸化糖缀合物和二硫键还原剂青霉素胺对其的释放能力。在初始悬浮液中、与体外培养的输卵管上皮结合的精子中和释放的精子中分析了尾部附睾精子表面蛋白的巯基。结果表明，附睾精子能够在体外结合输卵管上皮，尽管程度低于冷冻解冻的射出精子；这种相互作用是由输卵管细胞微绒毛介导的，微绒毛紧密结合精子头部的质膜，正如先前对射出精子的研究所示。硫酸化糖缀合物肝素、褐藻糖胶和硫酸葡聚糖以及二硫键还原剂青霉素胺都是强有力的精子释放诱导剂。精子表面蛋白巯基的水平为：（1）在初始精子悬浮液中较高；（2）在结合的精子中较低；（3）在肝素或青霉素胺释放的精子中显著增加。总之，附睾精子已经能够结合输卵管上皮，并通过将精子表面蛋白二硫键还原为巯基来响应释放诱导剂。
