Increased pituitary response to somatostatin in aging male rats: relationship to somatostatin receptor number and affinity.
Increased pituitary response to somatostatin in aging male rats: relationship to somatostatin receptor number and affinity.
复制标题
老年雄性大鼠垂体对生长抑素的反应增加：与生长抑素受体数量和亲和力的关系。
DOI：
10.1159/000125269
复制
发表时间：
1989
影响因子：
4.1
通讯作者：
Sonntag,WE
中科院分区：
文献类型：
--
作者：
Spik,K;Sonntag,WE
先前的研究已经证实，生长激素脉冲幅度随着年龄的增长而下降。本研究的目的是确定这种下降是否与（1）垂体对生长抑素的反应增加和/或（2）垂体生长抑素受体的数量或亲和力增加有关。在第一项研究中，年轻（3-4 个月）、中年（12-14 个月）和老年（22-24 个月）雄性 Fischer 344 大鼠的垂体切片灌注了基本必需培养基（1 ml/min），并以 5 分钟的间隔收集组分。用 10–7MhpGRF (1–44) 刺激组织 1 分钟，40 分钟后，在 5 × 10–9Msomatostatin-14 或 somatostatin-28 存在的情况下用 hpGRF 刺激组织。每个年龄组的两个垂体同时进行超融合，实验重复4次。通过放射免疫测定法测量生长激素释放。在第二项研究中，使用 iodo-[Tyr⁰]-D-Trp8somatostatin-14 比较了三个年龄组的纯化垂体膜中的生长抑素受体。将来自每个年龄组的动物合并，提取膜，并与增加剂量的冷肽一起孵育。通过Scatchard分析来分析结合特性并计算Ka和Bmax。结果表明，(1) 基础生长激素释放随着年龄和生长激素抑制素给药而减少，(2) 当数据表示为相对于基线的增加百分比时，所有年龄组中 GRF 诱导的生长激素释放相似，(3) 在生长激素抑制素 14 存在的情况下，与年轻或中年大鼠相比，老年大鼠中 GRF 诱导的生长激素释放减弱 (p < 0.01)。尽管生长抑素受体的数量和亲和力似乎随着年龄的增长而减少，但这些差异并不具有统计学意义。我们得出的结论是，垂体对生长抑素反应的受体后变化导致生长激素释放随着年龄的增长而减少。
Previous research has established that growth hormone pulse amplitude declines with increasing age. The purpose of this study was to determine whether this decline is associated with (1) increased pituitary response to somatostatin, and/or (2) increased number or affinity of pituitary somatostatin receptors. In the first study, pituitary slices from young (3–4 months), middle-aged (12–14 months), and old (22–24 months) male Fischer 344 rats were superfused with minimal essential medium (1 ml/min) and fractions collected at 5-min intervals. Tissues were stimulated with 10–7MhpGRF (1–44) for 1 min and, 40 min later, with hpGRF in the presence of 5 × 10–9Msomatostatin-14 or somatostatin-28. Two pituitaries from each age group were super-fused simultaneously and the experiment replicated 4 times. Growth hormone release was measured by radioimmunoassay. In a second study, somatostatin receptors in purified pituitary membranes from the three age groups were compared using iodo-[Tyr⁰]-D-Trp8somatostatin-14. Animals from each age group were pooled, membranes extracted, and incubated with increasing doses of cold peptide. Binding characteristics were analyzed by Scatchard analysis and Ka and Bmaxcalculated. Results indicated that (1) basal growth hormone release diminished both with age and somatostatin administration, (2) GRF-induced release of growth hormone was similar in all age groups when data were expressed as percent increase from baseline, and (3) in the presence of somatostatin-14, GRF-induced release of growth hormone was attenuated in old as compared to young or middle-aged rats (p < 0.01). Although somatostatin receptor number and affinity appeared to diminish with age, these differences were not statistically significant. We conclude that postreceptor changes in pituitary response to somatostatin contribute to diminished growth hormone release with age.