Milenkovic L, McCann S M
Department of Physiology, University of Texas Southwestern Medical Center, Dallas 75235-9040.
Neuroendocrinology. 1992 Jan;55(1):14-9. doi: 10.1159/000126091.
The thymosins are a family of hormone-like products of epithelial cells of the thymus which are important in maintenance and function of the immune system. Thymosin fraction 5, a partially purified extract of calf thymus, can influence pituitary hormone release. We have studied the effects of thymosin alpha 1 (T alpha 1), the first peptide isolated from thymosin fraction 5, on thyrotropin (TSH), adrenocorticotropin (ACTH), prolactin (Prl) and growth hormone (GH) release. To evaluate its effect in vivo we injected the peptide into the third ventricle of conscious male rats and measured the concentration of the pituitary hormones in plasma at different times after the injection. Following third-ventricular injection of T alpha 1, there was a significant decrease in plasma TSH and ACTH concentrations in comparison with values of control groups injected with diluent. The decrease in plasma TSH was of longer duration and was obtained with a lower dose of T alpha 1 than that of ACTH. Also, a significant decrease in plasma Prl was observed, with the same dose as for TSH. On the other hand, there were no significant changes in plasma GH. To examine if there is any direct effect of T alpha 1 at the pituitary level, we incubated hemipituitaries from male rats in vitro with different concentrations of the peptide. In this system T alpha 1 evoked a dose-dependent release of TSH and ACTH, while there was no effect on the release of Prl and GH.(ABSTRACT TRUNCATED AT 250 WORDS)
胸腺素是胸腺上皮细胞产生的一类激素样物质，对免疫系统的维持和功能很重要。胸腺素组分5是从小牛胸腺中部分纯化得到的提取物，能影响垂体激素的释放。我们研究了从胸腺素组分5中分离出的首个肽胸腺素α1（Tα1）对促甲状腺激素（TSH）、促肾上腺皮质激素（ACTH）、催乳素（Prl）和生长激素（GH）释放的影响。为评估其体内作用，我们将该肽注入清醒雄性大鼠的第三脑室，并在注射后不同时间测量血浆中垂体激素的浓度。第三脑室注射Tα1后，与注射稀释剂的对照组相比，血浆TSH和ACTH浓度显著降低。血浆TSH降低的持续时间更长，且产生该效应所需的Tα1剂量低于ACTH。同样，与TSH相同剂量时，血浆Prl也显著降低。另一方面，血浆GH无显著变化。为检测Tα1在垂体水平是否有直接作用，我们将雄性大鼠的半垂体在体外与不同浓度的该肽一起孵育。在这个系统中，Tα1引起TSH和ACTH的剂量依赖性释放，而对Prl和GH的释放没有影响。（摘要截短于250词）
