Rose R W, Kuswanti Nur
School of Zoology, University of Tasmania, Private Bag 5, Hobart, Tasmania 7001, Australia.
Gen Comp Endocrinol. 2004 Mar;136(1):17-22. doi: 10.1016/j.ygcen.2003.11.007.
The Tasmanian bettong (Bettongia gaimardi) is a small rat-kangaroo (marsupial) found only in Tasmania, Australia. The duration of pouch life is 15 weeks. Adults and older young display non-shivering thermogenesis and this paper examines the role of thyroxine in the development of endothermy in pouch young. Free thyroxine (T4) concentrations varied throughout pouch life. The mean (+/-SE) concentration was 6.2+/-1.9 pmol L(-1) in week 7, increased and peaked at 19.2+/-4.3 pmol L(-1) in week 12, and declined to 5.6+/-0.4 pmol L(-1) by week 20. This was similar to adult levels (3.2+/-3.8 pmol L(-1)). These concentrations showed significant differences. From pouch week 12 onwards, T4 injection raised oxygen consumption. Maximum levels of VO2 after T4 injection occurred at weeks 14-15. Although adult levels were lower, the increase in adult oxygen consumption after T4 injection was about 50%. Peak free T4 levels and metabolic responses to nor-adrenalin occur at week 12 and we hypothesize that thyroid hormone may facilitate the development of adrenergic-receptors in this species. The data presented in the paper further attest to the likely important role of the thyroid gland in the development of endothermy in marsupial pouch young.
袋獾（Bettongia gaimardi）是一种小型的鼠袋鼠（有袋动物），仅在澳大利亚塔斯马尼亚岛被发现。育儿袋生活期为15周。成年个体和稍大的幼崽会进行非颤抖性产热，本文研究了甲状腺素在育儿袋幼崽体温调节发育中的作用。游离甲状腺素（T4）浓度在育儿袋生活期内有所变化。第7周时平均（±标准误）浓度为6.2±1.9 pmol/L⁻¹，在第12周时升高并达到峰值19.2±4.3 pmol/L⁻¹，到第20周时降至5.6±0.4 pmol/L⁻¹。这与成年个体水平（3.2±3.8 pmol/L⁻¹）相似。这些浓度存在显著差异。从育儿袋第12周起，注射T4会提高耗氧量。注射T4后VO₂的最高水平出现在第14 - 15周。虽然成年个体水平较低，但注射T4后成年个体耗氧量的增加约为50%。游离T4峰值水平和对去甲肾上腺素的代谢反应出现在第12周，我们推测甲状腺激素可能促进了该物种肾上腺素能受体的发育。本文所呈现的数据进一步证明了甲状腺在有袋动物育儿袋幼崽体温调节发育中可能发挥的重要作用。
