Karabinus D S, Vogler C J, Saacke R G, Evenson D P
Department of Chemistry, South Dakota State University, Brookings, USA.
J Androl. 1997 Sep-Oct;18(5):549-55.
The reported effects on semen quality ascribed to testicular heat stress generally relate to traits impacting sperm transport and fertilizing ability but not to the genetic material contained by the sperm. To characterize the effects of testicular heat stress on sperm chromatin, susceptibility of DNA in sperm nuclear chromatin to in situ acid denaturation was measured by flow cytometry after staining with acridine orange using the sperm chromatin structure assay (SCSA). Semen was collected from Holstein bulls at 3-day intervals, before and after 48-hour scrotal insulation, until the morphologically abnormal sperm content in raw semen exceeded 50%. After cryopreservation in egg yolk-citrate extender, semen was thawed and sampled during incubation in vitro at 38.5 degrees C. Overall, SCSA results showed that chromatin susceptibility to denaturation was increased for sperm collected post- vs. preinsulation and was more pronounced for sperm presumably in the testes during insulation than for those sperm presumably in the epididymides. Increased susceptibility was detected as early as the first collection postinsulation; however, chromatin of sperm presumably in the proximal epididymis during insulation did not appear to have been detrimentally affected. Chromatin susceptibility to denaturation increased with increased incubation time in vitro, but the rate of change in susceptibility during incubation did not differ among pre- vs. postinsulation specimens. We conclude that elevated scrotal temperatures adversely affect both epididymal and testicular sperm by reducing sperm chromatin stability. The effects of heat stress on the chromatin of epididymal sperm were more subtle than those exhibited by testicular sperm but detectable within close proximity to the heat stress event.
据报道，睾丸热应激对精液质量的影响通常与影响精子运输和受精能力的特征有关，而与精子所含的遗传物质无关。为了表征睾丸热应激对精子染色质的影响，使用精子染色质结构分析（SCSA），在用吖啶橙染色后，通过流式细胞术测量精子核染色质中DNA对原位酸变性的敏感性。在48小时阴囊保温前后，每隔3天从荷斯坦公牛采集精液，直到原精液中形态异常精子含量超过50%。在卵黄柠檬酸盐稀释液中冷冻保存后，精液解冻并在38.5℃体外孵育期间取样。总体而言，SCSA结果表明，保温后采集的精子与保温前相比，染色质对变性的敏感性增加，并且对于保温期间可能在睾丸中的精子比对于可能在附睾中的精子更明显。早在保温后的第一次采集就检测到敏感性增加；然而，保温期间可能在附睾近端的精子染色质似乎没有受到不利影响。染色质对变性的敏感性随着体外孵育时间的增加而增加，但孵育期间敏感性的变化率在保温前和保温后的样本之间没有差异。我们得出结论，阴囊温度升高通过降低精子染色质稳定性对附睾和睾丸精子均产生不利影响。热应激对附睾精子染色质的影响比睾丸精子表现出的影响更微妙，但在接近热应激事件时可检测到。
