Goya R G, Quigley K L, Takahashi S, Reichhart R, Meites J
Department of Physiology, Michigan State University, East Lansing 48824.
Mech Ageing Dev. 1989 Aug;49(2):119-28. doi: 10.1016/0047-6374(89)90095-x.
There is increasing evidence that the neuroendocrine system is responsive to hormonal signals generated by the immune system. Thus, interleukin-1, hepatocyte stimulating factor and thymosin have been shown to stimulate adrenocorticotropin, beta-endorphin and luteinizing hormone secretion. We report here that homeostatic thymus hormone (HTH), a well-characterized thymic preparation, reduces plasma thyrotropin (TSH) and growth hormone (GH) in young (3 months) Sprague-Dawley male rats, but fails to do so (TSH) or has a significantly weaker effect (GH) in old (26 months) animals. Young and old conscious, free-moving rats carrying an indwelling atrial cannula received the substances to be tested via the cannulas. Plasma samples were taken every 30 min for 5 h and hormones were measured by RIA. In the young rats, HTH (8 mg/kg body wt) induced a marked reduction in plasma TSH which was significantly greater than the normal circadian decline observed in saline-injected young controls. The old rats displayed high basal levels of TSH which showed no circadian rhythmicity and did not respond to HTH. Plasma thyroxine (T4) showed a significant age-related reduction but was not affected by HTH. The above dose of HTH significantly reduced plasma GH in young and old rats, but the effect was greater in the young animals. Mean basal levels of plasma GH were significantly lower in old than in young rats. The present results suggest that HTH, whose production by the thymus is known to be stimulated by TSH and GH, is involved in an inhibitory feedback loop regulating plasma TSH and GH in young rats. Our data also suggest an age-related desensitization of the TSH and GH systems to thymic influence in this species.
越来越多的证据表明，神经内分泌系统对免疫系统产生的激素信号有反应。因此，白细胞介素 -1、肝细胞刺激因子和胸腺素已被证明可刺激促肾上腺皮质激素、β -内啡肽和促黄体生成素的分泌。我们在此报告，稳态胸腺激素（HTH），一种特性明确的胸腺制剂，可降低年轻（3个月）的斯普拉格 - 道利雄性大鼠的血浆促甲状腺激素（TSH）和生长激素（GH），但在老年（26个月）动物中对TSH无此作用或对GH的作用明显较弱。携带留置心房插管的年轻和老年清醒、自由活动的大鼠通过插管接受待测试的物质。每30分钟采集一次血浆样本，共采集5小时，并通过放射免疫分析法测定激素。在年轻大鼠中，HTH（8毫克/千克体重）可使血浆TSH显著降低，这明显大于在注射生理盐水的年轻对照中观察到的正常昼夜节律性下降。老年大鼠的TSH基础水平较高，无昼夜节律，且对HTH无反应。血浆甲状腺素（T4）显示出与年龄相关的显著降低，但不受HTH影响。上述剂量的HTH可显著降低年轻和老年大鼠的血浆GH，但对年轻动物的作用更大。老年大鼠血浆GH的平均基础水平明显低于年轻大鼠。目前的结果表明，已知其产生受TSH和GH刺激的HTH参与了调节年轻大鼠血浆TSH和GH的抑制性反馈回路。我们的数据还表明，该物种的TSH和GH系统对胸腺影响存在与年龄相关的脱敏现象。
