Sugihara H, Minami S, Okada K, Kamegai J, Hasegawa O, Wakabayashi I
Department of Medicine, Nippon Medical School, Tokyo, Japan.
Endocrinology. 1993 Mar;132(3):1225-9. doi: 10.1210/endo.132.3.7679974.
To examine whether somatostatin (SS) exerts influences on the steady state levels of GH-releasing factor (GRF), the effect of SS on GH gene transcription was examined in rats. This approach was used because it has been shown that GRF stimulates GH gene transcription independent of GH release, and SS does not inhibit basal or GRF-stimulated GH gene transcription. Therefore, it is assumed that an effect of SS on GH gene transcription would be mediated by a change in GRF levels. Adult female Sprague-Dawley rats were provided with right atrial cannulae. Studies were performed using unanesthetized rats. Pituitary GH gene transcription was measured by transcription assay. An iv administration of antiserum to rat GRF 150 min previously significantly decreased GH gene transcription compared with that in control rats given normal goat serum. A continuous infusion of SS (300 micrograms/kg.h) via the cannula for 150 min significantly decreased GH gene transcription compared with that in control rats receiving 0.9% NaCl. When GRF (3 micrograms/kg.h) was given simultaneously with SS (300 micrograms/kg.h), GH gene transcription increased significantly compared with that in rats receiving SS infusion alone. After the withdrawal of SS infusion, GH gene transcription rapidly and significantly increased. The data suggest that SS reduces the steady state levels of GRF.
为研究生长抑素（SS）是否对生长激素释放因子（GRF）的稳态水平产生影响，我们在大鼠中检测了SS对生长激素（GH）基因转录的作用。采用该方法是因为已有研究表明，GRF可独立于GH释放刺激GH基因转录，且SS不抑制基础或GRF刺激的GH基因转录。因此，推测SS对GH基因转录的影响是由GRF水平的变化介导的。给成年雌性Sprague-Dawley大鼠植入右心房插管。实验在未麻醉的大鼠身上进行。通过转录分析测定垂体GH基因转录。与给予正常山羊血清的对照大鼠相比，150分钟前静脉注射抗大鼠GRF抗血清显著降低了GH基因转录。通过插管持续输注SS（300微克/千克·小时）150分钟，与接受0.9%氯化钠的对照大鼠相比，显著降低了GH基因转录。当GRF（3微克/千克·小时）与SS（300微克/千克·小时）同时给予时，与单独接受SS输注的大鼠相比，GH基因转录显著增加。停止输注SS后，GH基因转录迅速且显著增加。这些数据表明，SS降低了GRF的稳态水平。
