Data from: Maternal stress-associated cortisol stimulation may protect embryos from cortisol excess in zebrafish

Abnormal embryo cortisol level causes developmental defects and poor survival in zebrafish (Danio rerio). However, no study has demonstrated that maternal stress leads to higher embryo cortisol content in zebrafish. We tested the hypothesis that maternal stress-associated elevation in cortisol levels increases embryo cortisol content in this asynchronous breeder. Zebrafish mothers were fed cortisol-spiked food for 5 days, to mimic maternal stress, followed by daily breeding for 10-days to monitor temporal embryo cortisol content. Cortisol treatment increased mean embryo yield, but the daily fecundity were variable among the groups. Embryo cortisol content was variable in both groups over a 10 d period. A transient elevation in cortisol levels was observed in the embryos from cortisol fed mothers only on day 3, but not on subsequent days. We tested whether excess cortisol stimulates 11βHSD2 expression in ovarian follicles as a means to regulate embryo cortisol deposition. Cortisol treatment in vitro increased 11βHSD2 levels 7-fold, and this expression was regulated by actinomycin D and cyclohexamide suggesting tight regulation of cortisol levels in the ovarian follicles. We hypothesize that cortisol-induced upregulation of 11βHSD2 activity in the ovarian follicles is a mechanism restricting excess cortisol incorporation into the eggs during maternal stress.胚胎皮质醇水平异常会导致斑马鱼（Danio rerio）出现发育缺陷与存活率降低。然而，目前尚无研究证实斑马鱼的母体应激会使其胚胎皮质醇含量升高。我们针对“母体应激相关的皮质醇水平升高会提升这种异步繁殖亲本的胚胎皮质醇含量”这一假说开展了验证。我们通过给斑马鱼母体投喂添加了皮质醇的饲料连续5天以模拟母体应激，随后连续10天每日进行产卵繁殖，以监测胚胎皮质醇含量的动态变化。皮质醇处理提升了平均胚胎产出量，但各组的每日产卵量存在波动。在10天的实验周期内，两组胚胎的皮质醇含量均存在波动。仅在实验第3天，投喂皮质醇饲料的母体所产胚胎的皮质醇水平出现一过性升高，后续天数未观察到此现象。我们验证了过量皮质醇是否会通过刺激卵巢滤泡中11β-羟基类固醇脱氢酶2（11βHSD2）的表达，以此调控胚胎皮质醇的沉积过程。体外皮质醇处理可使11βHSD2的表达水平上调7倍，且该表达受放线菌素D（actinomycin D）与环己酰亚胺（cyclohexamide）调控，这表明卵巢滤泡内的皮质醇水平受到严格调控。我们据此提出假说：母体应激期间，卵巢滤泡内皮质醇诱导的11βHSD2活性上调，是限制过量皮质醇进入卵母细胞的调控机制。