Buaboocha W, Gemmell R T
Department of Anatomical Sciences, University of Queensland, St. Lucia, Brisbane, Australia.
Growth Dev Aging. 1996 Autumn-Winter;60(3-4):163-9.
The brushtail possum, Trichosurus vulpecula, produces a single offspring 200 mg in body weight. The young grow slowly during the first half of pouch of life at approximately 1g/day. At day 96 post partum the growth rate increases dramatically and it has been suggested that this change in growth rate may result from the initiation of thyroid function in the young possum. To determine the role of the thyroid gland of the possum on growth, the production of hormones from the thyroid was inhibited by administration of the drug, methimazole. The drug was administered to adult and young possums at day 140 post partum for 28 days and to young at day 100 post partum for 42 days and the effects of this treatment on plasma concentrations of thyroxine and on growth were monitored. Methimazole was found to inhibit thyroxine production in 4 of the 6 adult possums although it had no effect on body weight. Similar treatment administered to nine young possums inhibited growth. The three surviving methimazole possum young treated at 100 days post partum weighed less than control possums after day 163 post partum. The four young treated at 140 days post partum also showed depression in growth rate. However, the depression was not as marked as that of the 100 day treated possums. It is highly likely therefore that the surge in growth rate in the possum at day 96 post partum is initiated by thyroxine produced by the thyroid gland of the young.
帚尾袋貂（Trichosurus vulpecula）每次产仔一只，出生时体重为200毫克。幼崽在育儿袋生活的前半段生长缓慢，每天增重约1克。产后第96天，其生长速度急剧增加，有人认为这种生长速度的变化可能是由于幼袋貂甲状腺功能开始发挥作用所致。为了确定袋貂甲状腺在生长过程中的作用，通过给予药物甲巯咪唑来抑制甲状腺激素的分泌。在产后第140天给成年和幼年袋貂服用该药物，持续28天；给产后第100天的幼年袋貂服用42天，并监测这种处理对甲状腺素血浆浓度和生长的影响。结果发现，6只成年袋貂中有4只的甲状腺素分泌受到抑制，尽管对体重没有影响。对9只幼年袋貂进行类似处理后抑制了其生长。产后第100天接受甲巯咪唑处理的3只存活的幼年袋貂，在产后第163天之后体重低于对照袋貂。产后第140天接受处理的4只幼年袋貂的生长速度也出现了下降。然而，这种下降不如100天接受处理的袋貂明显。因此，很有可能产后第96天袋貂生长速度的激增是由幼崽甲状腺产生的甲状腺素引发的。
