Weiss Stacey L, Johnston Gwynne, Moore Michael C
School of Life Sciences, Arizona State University, Tempe, AZ 85287-1505, USA.
Comp Biochem Physiol A Mol Integr Physiol. 2007 Mar;146(3):360-5. doi: 10.1016/j.cbpa.2006.11.009. Epub 2006 Nov 24.
The regulation of hatching in oviparous animals is important for successful reproduction and survival, but is poorly understood. We unexpectedly found that RU-486, a progesterone and glucocorticoid antagonist, interferes with hatching of viable tree lizard (Urosaurus ornatus) embryos in a dose-dependent manner and hypothesized that embryonic glucocorticoids regulate hatching. To test this hypothesis, we treated eggs with corticosterone (CORT) or vehicle on Day 30 (85%) of incubation, left other eggs untreated, and observed relative hatch order and hatch time. In one study, the CORT egg hatched first in 9 of 11 clutches. In a second study, the CORT egg hatched first in 9 of 12 clutches, before vehicle-treated eggs in 10 of 12 clutches, and before untreated eggs in 7 of 9 clutches. On average, CORT eggs hatched 18.2 h before vehicle-treated eggs and 11.6 h before untreated eggs. Thus, CORT accelerates hatching of near-term embryos and RU-486 appears to block this effect. CORT may mobilize energy substrates that fuel hatching and/or accelerate lung development, and may provide a mechanism by which stressed embryos escape environmental stressors.
卵生动物孵化的调控对于成功繁殖和生存至关重要，但目前人们对此了解甚少。我们意外地发现，孕酮和糖皮质激素拮抗剂RU-486以剂量依赖的方式干扰了有活力的鬃狮蜥（Urosaurus ornatus）胚胎的孵化，并推测胚胎糖皮质激素调节孵化过程。为了验证这一假设，我们在孵化的第30天（85%）用皮质酮（CORT）或溶剂处理卵，其余卵不做处理，然后观察相对孵化顺序和孵化时间。在一项研究中，11窝卵中有9窝的CORT处理卵最先孵化。在第二项研究中，12窝卵中有9窝的CORT处理卵最先孵化，在12窝中有10窝先于溶剂处理卵孵化，在9窝中有7窝先于未处理卵孵化。平均而言，CORT处理卵比溶剂处理卵提前18.2小时孵化，比未处理卵提前11.6小时孵化。因此，CORT加速了近足月胚胎的孵化，而RU-486似乎阻断了这种作用。CORT可能动员为孵化提供能量的底物和/或加速肺部发育，并且可能提供一种机制，使处于应激状态的胚胎能够逃避环境应激源。
