Department of Animal Science, Institute of Agriculture, UT AgResearch, The University of Tennessee, Knoxville, Tennessee 37996-4574, USA.
Reproduction. 2011 Dec;142(6):831-43. doi: 10.1530/REP-11-0032. Epub 2011 Oct 12.
Consequences of heat stress exposure during the first 12 h of meiotic maturation differed depending on how and when bovine oocytes were activated. If heat-stressed oocytes underwent IVF at ~24 h, blastocyst development was less than for respective controls and similar to that obtained for nonheat-stressed oocytes undergoing IVF at 30 h (i.e. slightly aged). In contrast, if heat-stressed oocytes underwent chemical activation with ionomycin/6-dimethylaminopurine at 24 h, blastocyst development was not only higher than respective controls, but also equivalent to development obtained after activation of nonheat-stressed oocytes at 30 h. Developmental differences in chemically activated vs IVF-derived embryos were not related to fertilization failure or gross alterations in cytoskeletal components. Rather, ionomycin-induced calcium release and MAP kinase activity were less in heat-stressed oocytes. While underlying mechanisms are multifactorial, ability to obtain equivalent or higher development after parthenogenetic activation demonstrates that oocytes experiencing heat stress during the first 12 h of meiotic maturation have the necessary components to develop to the blastocyst stage, but fail to do so after fertilization.
热应激暴露对卵母细胞减数分裂成熟后 12 小时内的影响因牛卵母细胞的激活方式和时间而异。如果热应激卵母细胞在大约 24 小时时进行 IVF，囊胚发育则不如相应对照组，与在 30 小时时进行 IVF 的非热应激卵母细胞（即轻度老化）的囊胚发育相当。相反，如果热应激卵母细胞在 24 小时时用离子霉素/6-二甲基氨基嘌呤进行化学激活，囊胚发育不仅高于相应对照组，而且与在 30 小时时激活非热应激卵母细胞获得的发育相当。化学激活和 IVF 衍生胚胎之间的发育差异与受精失败或细胞骨架成分的明显改变无关。相反，热应激卵母细胞中离子霉素诱导的钙释放和 MAP 激酶活性较低。虽然潜在的机制是多因素的，但在孤雌激活后仍能获得相当或更高的发育能力表明，在减数分裂成熟的前 12 小时经历热应激的卵母细胞具有发育到囊胚阶段的必要成分，但在受精后却无法发育。
