Florini J R, Harned J A, Richman R A, Weiss J P
Mech Ageing Dev. 1981 Feb;15(2):165-76. doi: 10.1016/0047-6374(81)90072-5.
The somatomedins are a family of hormones which appear to mediate many of the anabolic actions of growth hormone; these processes often exhibit an age-associated deterioration in intact animals. We have demonstrated the validity of a radioreceptor assay for the determination of somatomedin levels in rat serum. In this assay, we measure displacement of 125I-labeled Multiplication Stimulating Activity (MSA) from receptors prepared from human placental membranes. Results with this procedure confirm and extend a previous report from this laboratory indicating a significant decrease in somatomedin levels during the latter part of the lifespan. Data are presented to eliminate possible artifactual explanations for the observed age-related changes. Furthermore, we find that the decrease in somatomedin levels can not be a simple result of an age-related decrease in basal levels of growth hormone in serum. We conclude that the decrease with age in circulating levels of the somatomedins is most probably attributable to a decrease in the activity of responsiveness of the tissues (most probably liver) which secrete somatomedins in response to stimulation by growth hormone.
生长调节素是一类激素，它们似乎介导了生长激素的许多合成代谢作用；在完整动物中，这些过程常常呈现出与年龄相关的衰退。我们已经证明了一种放射受体测定法在测定大鼠血清中生长调节素水平方面的有效性。在该测定法中，我们测量从人胎盘膜制备的受体上125I标记的增殖刺激活性（MSA）的位移。该方法的结果证实并扩展了本实验室先前的一份报告，该报告表明在寿命后期生长调节素水平显著下降。提供的数据排除了对观察到的与年龄相关变化的可能人为解释。此外，我们发现生长调节素水平的下降并非血清中生长激素基础水平与年龄相关下降的简单结果。我们得出结论，生长调节素循环水平随年龄下降很可能归因于分泌生长调节素以响应生长激素刺激的组织（很可能是肝脏）的活性或反应性降低。
