期刊
JOURNAL OF COMPARATIVE PHYSIOLOGY B-BIOCHEMICAL SYSTEMIC AND ENVIRONMENTAL PHYSIOLOGY
卷 171, 期 2, 页码 113-119出版社
SPRINGER-VERLAG
DOI: 10.1007/s003600000155
关键词
iopanoic acid; seasonality; sparrows; thyroxine; triiodothyronine
This study tested the hypothesis that L-3.5,3'-triiodothyronine (T-3) is the bioactive seasonality thyroid hormone in American tree sparrows (Spizella arborea). The experimental approach coupled thyroid hormone replacement therapy after radiothyroidectomy with photostimulation and intracerebroventricular infusion of iopanoic acid, an inhibitor of L-3.5.3'-triiodothyronine synthesis and degradation. Endpoints were testis length, molt score, and hypothalamic content of chicken gonadotropin-releasing hormone I. The hypothesis predicts that thyroidectomized male tree sparrows moved to long days and given thyroxine in combination with iopanoic acid will lack L-3,5,3'-triiodothyronine and so will not express thyroid hormone-dependent photoperiodic testicular growth (a vernal component of seasonality) and photorefracturiness or postnuptial molt (autumnal components of seasonality). It further predicts that iopanoic acid will enhance the efficacy of L-3,5,3'-triiodothyronine and so will facilitate the expression of seasonality in thyroidectomized males given L-3,5,3'-triiodothyronine replacement therapy. Iopanoic acid had no significant effect on any component of seasonality in thyroid-intact males given vehicle, or in thyroidectomized males given thyroxine or L-3,5,3'-triiodothyronine. Thyroid-intact males, as well as thyroidectomized males infused with thyroxine alone, commonly expressed all components of seasonality. Thyroidectomized males given L-3,5,3'-triiodothyronine alone exhibited photoperiodic testicular growth, but did not become photorefractory or initiate molt. While these results confirm that thyroid hormone acts centrally to program American tree sparrows for seasonality, they do not support the hypothesis that L-3,5,3'-triiodothyronine is the bioactive seasonality thyroid hormone. and they challenge the view that thyroxine is merely a prohormone.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据