Ontogeny of thyroid hormone receptors in the brushtail possum (Trichosurus vulpecula)

Reproduction, Fertility, and Development
C SerniaR T Gemmell

Abstract

Newborn marsupials do not have a thyroid gland at birth. The gland develops while the young marsupial is in the mother's pouch. The young brushtail possum initiates secretion of thyroid hormones from its own thyroid at about Day 65 post partum. However, during the first three weeks of pouch life thyroxine is passed from the mother to the young via the milk. To determine if this maternal thyroxine can effect organ development in the young possum before it initiates secretion of thyroxine from its own thyroid, the ontogeny of thyroid hormone receptors was determined in nuclear extracts of lung, liver and kidney by radioreceptor assay, using (125)I-labelled tri-iodothyronine as ligand. Receptor density was calculated for tissues removed from young possums at Days 25 (n = 5), 50 (n = 4), 100 (n = 3) and 150 (n = 4) and from adults (n = 5). Receptors were found in possums of all age groups, including the small 25-day pouch young. Significant differences were not found in the receptor density between different tissues or at various ages. The association constant Ka (4.0+/-2.6 L nmol[-1] for lung) was similar in different tissues and at the various ages examined. The passage of thyroid hormones from the mother to the developing marsup...Continue Reading

Citations

Aug 31, 2001·ILAR Journal·Paul B. Samollow
Oct 10, 2015·General and Comparative Endocrinology·Christine Elizabeth Cooper
Jun 20, 2006·Respiratory Physiology & Neurobiology·P B Frappell, P M MacFarlane

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