Fed Proc. 1975 Feb;34(2):183-5.
Splenic leukocytes of senescent rats (24-26 mo) exhibit a 60% reduction in cortisol-induced inhibition of 3-H-uridine uptake when compared to mature adult animals (12-14 mo). The degree of inhibition is directly proportional to cortisol dosage up to 2 X 10-6 M. Specific binding of physiological (nanomolar) concentrations of 3-H-cortisol by leukocytic cytosol macromolecules is reduced by over 40% in the older animals. Moreover, Scatchard analyses reveal 60% fewer specific glucocorticoid binding sites in the cytosols of cells from the senescent rats. Such analyses were performed in vitro at 0 C to eliminate metabolism of steroids. In addition, 3-H-dexamethasone was used instead of 3-H-cortisol to eliminate binding to plasma (or serum) transcortin. Inhibition of 3-H-uridine uptake requires specific glucocorticoid binding. The degree of inhibition at varying glucocorticoid dosages is proportional to the amount of specific binding to cytoplasmic macromolecules. Thus, age-related reduction in specific glucocorticoid binding sites may be at least partially responsible for altered responsiveness of splenic leukocytes to these hormones.
与成熟成年动物（12 - 14月龄）相比，衰老大鼠（24 - 26月龄）的脾脏白细胞在皮质醇诱导的对3 - H - 尿苷摄取的抑制方面表现出60%的降低。抑制程度与皮质醇剂量直接成正比，最高可达2×10 - 6 M。在老年动物中，白细胞胞浆大分子对生理（纳摩尔）浓度的3 - H - 皮质醇的特异性结合减少了40%以上。此外，Scatchard分析显示，衰老大鼠细胞胞浆中特异性糖皮质激素结合位点减少了60%。此类分析在0℃体外进行以消除类固醇的代谢。另外，使用3 - H - 地塞米松而非3 - H - 皮质醇以消除与血浆（或血清）皮质素转运蛋白的结合。3 - H - 尿苷摄取的抑制需要特异性糖皮质激素结合。不同糖皮质激素剂量下的抑制程度与与细胞质大分子的特异性结合量成正比。因此，与年龄相关的特异性糖皮质激素结合位点的减少可能至少部分导致了脾脏白细胞对这些激素反应性的改变。
