This study aimed to evaluate the effect of seminal plasma on bovine sperm cryopreservation and to assess the integrity of plasma and acrosomal membranes, mitochondrial potential, remodelling of F-actin cytoskeleton and sperm chromatin fragmentation during the cooling, equilibrium and freezing/thawing stages. Six ejaculates collected from seven Nelore bulls (n = 42) were used in this study. Each ejaculate was divided into two aliquots (with seminal plasma = SP group; without seminal plasma = NSP group) and packed to a final concentration of 50 × 10⁶ sperm per straw. Statistical analyses were performed using SAS software (version 9.3), and p ≤ .05 was considered significant. A time effect was observed for all sperm characteristics (p < .05), except for chromatin fragmentation (p > .05). The presence of seminal plasma better preserved the acrosomal integrity (SP = 75.2% and NSP = 71.7%; p < .05) and also provided lower F-actin remodelling during cryopreservation process (SP = 29.9% and NSP = 32.4%; p < .05). Regarding to the cryopreservation stages, it was observed that cooling step induced higher remodelling of F-actin than the equilibrium and freezing/thawing stages (56.3%, 32.2% and 23.9%, respectively; p < .05). The equilibrium step had minor influence on overall sperm characteristics while the freezing/thawing stage was responsible for the highest percentage of damage in plasma membrane (−65.2%), acrosomal membrane (−34.0%) and mitochondrial potential (−48.1%). On the other hand, none of the cryopreservation stages affected chromatin integrity. It was concluded that the presence of seminal plasma provides increased acrosomal integrity and reduced remodelling of F-actin cytoskeleton. Higher F-actin remodelling is observed after the cooling step while the freezing/thawing step is most damaging to sperm membranes and mitochondrial potential during bovine sperm cryopreservation.

中文翻译：

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精浆对牛精子冷冻保存不同阶段的影响

本研究旨在评估精浆对牛精子冷冻保存的影响，并评估血浆和顶体膜的完整性、线粒体潜力、F-肌动蛋白细胞骨架的重塑和精子染色质断裂在冷却、平衡和冷冻/解冻阶段。 本研究使用了从七头 Nelore 公牛 ( n = 42)收集的六份精液。每个射精被分成两等份（精浆= SP 组；没有精浆= NSP 组）并包装到每根吸管50 × 10 ^{6 个}精子的最终浓度。使用 SAS 软件（9.3 版）进行统计分析，p  ≤ .05 被认为是显着的。观察到所有精子特征的时间效应（p < .05)，染色质碎裂除外 ( p  > .05)。精浆的存在更好地保持了顶体完整性（SP = 75.2% 和 NSP = 71.7%；p  < .05），并且在冷冻保存过程中还提供了较低的 F-肌动蛋白重塑（SP = 29.9% 和 NSP = 32.4%；p  < .05）。关于冷冻保存阶段，观察到冷却步骤比平衡和冷冻/解冻阶段诱导了更高的 F-肌动蛋白重塑（分别为 56.3%、32.2% 和 23.9%；p < .05）。平衡步骤对整体精子特征的影响较小，而冷冻/解冻阶段对质膜 (-65.2%)、顶体膜 (-34.0%) 和线粒体电位 (-48.1%) 的损伤百分比最高。另一方面，没有一个冷冻保存阶段影响染色质的完整性。结论是精浆的存在提供了增加的顶体完整性和减少的 F-肌动蛋白细胞骨架的重塑。在冷却步骤后观察到更高的 F-肌动蛋白重塑，而冷冻/解冻步骤在牛精子冷冻保存过程中对精子膜和线粒体电位的破坏最大。