Azzam Milène A, Szdzuy Kirsten, Mortola Jacopo P
Department of Physiology, McGill University, Montreal, Quebec, Canada.
Am J Physiol Regul Integr Comp Physiol. 2007 Jun;292(6):R2373-9. doi: 10.1152/ajpregu.00885.2006. Epub 2007 Mar 8.
We asked to what extent sustained hypoxia during embryonic growth might interfere with the normal development of thermogenesis. White Leghorn chicken eggs were incubated at 38 degrees C either in normoxia (Nx, 21% O2) or in hypoxia [Hx, 15% O2, from embryonic day 5 (E5) until hatching]. The Hx embryos had lower body weight (W) throughout incubation, and hatching was delayed by about 10 h. For both groups, all measurements were conducted in normoxia. At embryonic day E11, the static temperature-oxygen consumption (ambient T-Vo2) curve was typically ectothermic (Q10 = 1.92-1.94) and similar between Nx and Hx. Toward the end of incubation (E20), the Q10 averaged 1.41 +/- 0.06 in Nx and 1.79 +/- 0.08 in Hx (P < 0.005), indicating that the onset of the thermogenic response in Hx lagged behind Nx. In the 1-day-old hatchlings (H1), body weight did not significantly differ between Nx and Hx. At H1, the T-Vo2 curves were endothermic-type, and more so in the older (>8 h old) than in the newly hatched (<8 h old) chicks, whether examined statically or dynamically as a function of time. In either case, the thermogenic responses of Hx were lower than those of Nx. In a 43-31 degrees C thermocline, the preferred T of the Hx hatchlings was around 37.3 degrees C, and similar to Nx, suggesting a similar setpoint for thermoregulation. We conclude that hypoxic incubation blunted the development of thermogenesis. This could be interpreted as an example of epigenetic regulation, in which an environmental perturbation during early development alters the phenotypic expression of a regulatory system.
我们研究了胚胎发育期间持续缺氧在多大程度上可能干扰正常的产热发育。将白来航鸡的鸡蛋在38摄氏度下孵化，分别处于常氧环境（Nx，21% O₂）或缺氧环境[Hx，15% O₂，从胚胎第5天（E5）直至孵化]。整个孵化过程中，Hx组胚胎的体重较低，孵化延迟约10小时。两组均在常氧环境下进行所有测量。在胚胎第11天（E11），静态温度-氧气消耗（环境温度-Vo₂）曲线通常为变温动物型（Q₁₀ = 1.92 - 1.94），Nx组和Hx组相似。接近孵化末期（E20），Nx组的Q₁₀平均为1.41 ± 0.06，Hx组为1.79 ± 0.08（P < 0.005），表明Hx组产热反应的起始落后于Nx组。在1日龄雏鸡（H1）中，Nx组和Hx组的体重无显著差异。在H1时，温度-Vo₂曲线为恒温动物型，对于较年长（>8小时龄）的雏鸡而言比新孵化（<8小时龄）的雏鸡更明显，无论是静态还是动态地作为时间的函数进行检测。在任何一种情况下，Hx组的产热反应均低于Nx组。在43 - 31摄氏度的温度梯度中，Hx组雏鸡的偏好温度约为37.3摄氏度，与Nx组相似，表明体温调节的设定点相似。我们得出结论，缺氧孵化会削弱产热的发育。这可以解释为表观遗传调控的一个例子，即早期发育期间的环境扰动会改变调节系统的表型表达。
