An atypical distribution of sperm acrosomal tyrosine-phosphorylated proteins [which include sperm acrosome associated 1 (SPACA1) proteins] may be related to the relatively lesser pregnancy rates when semen of some bulls are used for artificial insemination (AI). There may also be these associations with bull SPACA1 proteins that are translocated from the equatorial segment to the anterior part in the acrosomes during sperm maturation in the normally functioning epididymis. The aim of the present study, therefore, was assessment of the characteristics of bull SPACA1 proteins. Results from immunocytochemical evaluations indicate there were large variations in sperm percentages with typically distributed SPACA1 proteins in acrosomes of cauda epididymal sperm samples (7%–95%). These values were positively correlated with percentages of epididymal spermatozoa with typically distributed acrosomal tyrosine-phosphorylated proteins (r=0.8564, P<0.001). Results indicate there are individual differences in translocation of SPACA1 proteins in the epididymis during sperm maturation, and that SPACA1 protein is one of the main determinants for the typical distribution of acrosomal tyrosine-phosphorylated proteins. In addition, conception rates as a result of AI using cryopreserved spermatozoa tended to be associated with percentages of epididymal spermatozoa with typically distributed SPACA1 proteins. Results from sucrose gradient centrifugation fractionation experiments indicate SPACA1 proteins are sperm membrane raft-associated proteins. Based on these results, it is hypothesized that there is an association between bull subfertility when semen is used for AI and epididymal dysfunctions in the arrangement of membrane lipid rafts during sperm maturation.

当一些公牛的精液用于人工授精（AI）时，精子顶体酪氨酸磷酸化蛋白的非典型分布（包括与精子顶体相关的1（SPACA1）蛋白）可能与相对较低的妊娠率有关。在正常运作的附睾中，在精子成熟过程中，公牛SPACA1蛋白也可能与这些相关，这些蛋白从赤道段转移到顶体的前部。因此，本研究的目的是评估牛SPACA1蛋白的特征。免疫细胞化学评估的结果表明，附睾附睾精子样品顶体中通常分布有SPACA1蛋白的精子百分比存在较大差异（7％–95％）。r = 0.8564，P<0.001）。结果表明，精子成熟过程中附睾中SPACA1蛋白的移位存在个体差异，并且SPACA1蛋白是顶体酪氨酸磷酸化蛋白典型分布的主要决定因素之一。另外，由于使用冷冻保存的精子进行人工授精而导致的受孕率往往与附有典型分布的SPACA1蛋白的附睾精子的百分比有关。蔗糖梯度离心分离实验的结果表明SPACA1蛋白是与精子膜筏相关的蛋白。基于这些结果，假设精子用于AI时，公牛的不育性与精子成熟过程中膜脂筏排列中的附睾功能障碍之间存在关联。