McNichols M J, McNabb F M
Department of Biology, Virginia Polytechnic Institute and State University, Blacksburg 24061.
Gen Comp Endocrinol. 1988 Apr;70(1):109-18. doi: 10.1016/0016-6480(88)90099-8.
We compared the developmental pattern of thyroid function and its pituitary control in precocial Japanese quail and altricial Ring doves. We measured thyroid hormone (TH) content of thyroid glands (TG), TH concentrations in the serum, relative pituitary gland thyrotropin (PG-TSH) content, and the ability of the TG to respond to exogenous TSH as indicated by increases in TG-3',5'-monophosphate (cAMP) content or in serum TH concentrations. In embryonic quail there is considerable maturation of thyroid function prior to hatching. TG-TH content is low but detectable in Day 8 embryos; TG-TH content increases 300x between Day 8 and hatching (16.5-day incubation). Pituitary TSH is detectable by bioassay in quail on embryonic Day 8, with higher levels found closer to hatching. The TG of 8-day embryos responds to TSH injection by increased TG-cAMP content but the serum TH response to TSH does not appear until Day 9. Serum TH concentrations suggest that the TG is under pituitary control during the latter part of incubation. In doves most of the development of thyroid function and the maturation of its pituitary control occur after hatching and thus thyroid functional development is much later in doves than in quail. TG-TH content is extremely low in embryos and nestlings up to 3 days after hatching, increases slowly in nestlings up to Day 10, then increases sharply. Serum TH content is very low in embryos and rises steadily in nestlings to plateau after about Day 8. Pituitary TSH content, estimated by a quail bioassay, is undetectable in embryos and nestlings until Day 4 but increases thereafter. The TG does not respond (based on serum TH concentration) to TSH injection through the day of hatching (Day 16; mean incubation period of 16.5 days), but an increase in serum TH occurs in Day 2 nestlings in response to TSH injection. The magnitude of this response continues to increase during the first week after hatching.
我们比较了早成鸟日本鹌鹑和晚成鸟环颈鸽甲状腺功能的发育模式及其垂体调控。我们测量了甲状腺（TG）中的甲状腺激素（TH）含量、血清中的TH浓度、垂体促甲状腺激素（PG-TSH）的相对含量，以及TG对外源性TSH的反应能力，这通过TG-3',5'-单磷酸（cAMP）含量或血清TH浓度的增加来表示。在胚胎期的鹌鹑中，孵化前甲状腺功能有相当程度的成熟。8日龄胚胎的TG-TH含量较低但可检测到；在第8天到孵化（孵化期16.5天）之间，TG-TH含量增加了300倍。通过生物测定法在胚胎第8天的鹌鹑中可检测到垂体TSH，在接近孵化时水平更高。8日龄胚胎的TG对TSH注射的反应是TG-cAMP含量增加，但血清TH对TSH的反应直到第9天才出现。血清TH浓度表明，在孵化后期TG受垂体控制。在鸽子中，甲状腺功能的大部分发育及其垂体调控的成熟发生在孵化后，因此鸽子的甲状腺功能发育比鹌鹑晚得多。孵化前及孵化后3天内的胚胎和雏鸟的TG-TH含量极低，雏鸟在第10天前缓慢增加，然后急剧增加。胚胎中的血清TH含量非常低，雏鸟中在约第8天后稳步上升至平稳状态。通过鹌鹑生物测定法估计，胚胎和雏鸟直到第4天才可检测到垂体TSH含量，但此后会增加。直到孵化当天（第16天；平均孵化期16.5天），TG对TSH注射无反应（基于血清TH浓度），但在第2天的雏鸟中，TSH注射会导致血清TH增加。这种反应的幅度在孵化后的第一周内持续增加。
