Goya R G, Sosa Y E, Quigley K L, Gottschall P E, Goldstein A L, Meites J
Department of Physiology, Michigan State University, East Lansing.
Neuroendocrinology. 1988 May;47(5):379-83. doi: 10.1159/000124942.
Thymosin fraction 5 (TF-5), a partially purified thymic preparation, has been previously shown to have luteinizing-hormone-releasing-hormone-releasing activity in perfused rat hypothalamus as well as an in vivo stimulatory effect on the pituitary-adrenal axis in prepubertal monkeys. We report here the effect of TF-5 on the plasma levels of several hormones in female rats of different ages. Conscious free-moving Sprague-Dawley rats carrying an indwelling atrial cannula received a single dose of 5 mg/kg body weight of either bovine serum albumin (BSA) or TF-5 via cannula. In young (3-4) months and old (25 months) rats, thymosin induced a marked reduction of plasma thyrotropin (TSH) which was significantly greater than the normal circadian decline observed in the BSA-treated controls. Senescent females (34 months) displayed high basal levels of TSH which showed little circadian rhythmicity and did not respond to TF-5. Thyroxine (T4), triiodothyronine (T3), corticosterone, and prolactin levels were not affected by TF-5 at the dose levels tested. An age-dependent decrease in basal plasma levels of T4 but not T3 was observed in both BSA- and TF-5-treated rats. Young females given up to 10 mg BSA/kg body weight (i.v.) and noninjected controls had similar levels of the above hormones up to 3.5 h after BSA injection. These results suggest that the thymus has an inhibitory action on TSH in the rat, which is not mediated by the thyroid gland. Our results also suggest an age-related desensitization of the TSH system to thymic influence in this species.
胸腺素组分5（TF-5）是一种部分纯化的胸腺制剂，先前已证明其在灌注的大鼠下丘脑具有促黄体生成激素释放激素释放活性，并且对青春期前猴子的垂体-肾上腺轴具有体内刺激作用。我们在此报告TF-5对不同年龄雌性大鼠几种激素血浆水平的影响。携带留置心房插管的清醒自由活动的Sprague-Dawley大鼠通过插管接受单剂量5mg/kg体重的牛血清白蛋白（BSA）或TF-5。在年轻（3-4）个月和老年（25个月）大鼠中，胸腺素导致血浆促甲状腺激素（TSH）显著降低，这明显大于在BSA处理的对照中观察到的正常昼夜节律下降。衰老雌性（34个月）显示TSH基础水平高，昼夜节律性小，并且对TF-5无反应。在测试的剂量水平下，甲状腺素（T4）、三碘甲状腺原氨酸（T3）、皮质酮和催乳素水平不受TF-5影响。在BSA和TF-5处理的大鼠中均观察到基础血浆T4水平随年龄下降，但T3水平未下降。给予高达10mg BSA/kg体重（静脉注射）的年轻雌性和未注射的对照在BSA注射后长达3.5小时具有相似的上述激素水平。这些结果表明胸腺对大鼠的TSH具有抑制作用，这不是由甲状腺介导的。我们的结果还表明该物种中TSH系统对胸腺影响存在与年龄相关的脱敏现象。
