Developmental Integrative Biology Research Group, Department of Biological Sciences, University of North Texas, 1155 Union Circle #305220, Denton, TX, 76203, USA.
Department of Biology, State University of New York Potsdam, Potsdam, NY, 13676, USA.
J Comp Physiol B. 2018 Sep;188(5):843-853. doi: 10.1007/s00360-018-1166-1. Epub 2018 Jun 8.
Thyroid hormones are key regulators of avian metabolism and may play a significant role in development at hatching. To better understand the role of thyroid hormones in avian development, we examined autonomic control of heart rate and blood pressure while manipulating thyroid hormone levels in the late stage embryonic Pekin duck (Anas platyrhynchos domestica). Thyroid hormone levels were manipulated on day 24 of a 28-day incubation period with the thyroperoxidase inhibitor methimazole (MMI), triiodothyronine (T), or saline. On day 25 of incubation, autonomic tone on cardiovascular function was studied by injections of cholinergic and adrenergic receptor antagonists. Embryos from all treatment groups expressed a cholinergic and β-adrenergic tone on heart rate at this age. Cholinergic blockade with atropine produced a larger change in heart rate in the hyperthyroid animals compared with euthyroid animals. In response to β-adrenergic blockade, hyperthyroid conditions produced a larger decrease in heart rate compared with euthyroid animals, with no change in mean arterial blood pressure. In response to α-adrenergic blockade, mean arterial blood pressure decreased in the euthyroid animals and more developed hyperthyroid animals. Collectively, the data indicate that elevated levels of T can influence maturation of cholinergic and adrenergic receptor-mediated cardiovascular regulation in developing Pekin ducks near the end of incubation.
甲状腺激素是鸟类代谢的关键调节剂，在孵化时的发育中可能发挥重要作用。为了更好地了解甲状腺激素在禽类发育中的作用，我们在晚期胚胎北京鸭（Anas platyrhynchos domestica）中操纵甲状腺激素水平时，检查了心率和血压的自主控制。在 28 天孵化期的第 24 天，用甲状腺过氧化物酶抑制剂甲巯咪唑（MMI）、三碘甲状腺原氨酸（T）或生理盐水处理甲状腺激素水平。在孵化的第 25 天，通过注射胆碱能和肾上腺素能受体拮抗剂研究心血管功能的自主神经张力。在这个年龄段，所有处理组的胚胎都表现出心率的胆碱能和β-肾上腺素能张力。与甲状腺功能正常的动物相比，甲状腺功能亢进动物的心脏胆碱能阻断用阿托品产生的心率变化更大。β-肾上腺素能阻断后，甲状腺功能亢进动物的心率下降幅度大于甲状腺功能正常动物，平均动脉血压无变化。α-肾上腺素能阻断后，甲状腺功能正常动物和发育较好的甲状腺功能亢进动物的平均动脉血压下降。总的来说，这些数据表明，T 水平升高会影响孵化末期发育中的北京鸭的胆碱能和肾上腺素能受体介导的心血管调节的成熟。
