Weiss J, Cronin M J, Thorner M O
Department of Physiology, University of Virginia School of Medicine, Charlottesville 22908.
Am J Physiol. 1987 Nov;253(5 Pt 1):E508-14. doi: 10.1152/ajpendo.1987.253.5.E508.
Growth hormone (GH) is secreted as pulses in vivo. To understand the signals governing this periodicity, we have established a perifusion-based model of pulsatile GH release. Male rat anterior pituitaries were dispersed and perifused with pulses of human growth hormone-releasing factor-(1--40) (GHRF), with or without a continuous or discontinuous somatostatin tonus. An experiment was composed of a 1-h base-line collection followed by four 3-h cycles; each contained single or paired 10-min infusion(s) of 3 nM GHRF. In testing the impact of somatostatin, the protocol was identical except that 0.3 nM somatostatin was added 30 min into the base-line period and then was either continued throughout the study or withdrawn during the periods of GHRF infusion. GH base lines with somatostatin were lower than vehicle base lines (P less than 0.05). GHRF pulses generated consistent peaks of GH release between 200 and 300 ng. min-1. (10(7) cells)-1, and these peaks were not altered by continuous somatostatin. In contrast, withdrawal of somatostatin during GHRF administration elicited markedly higher GH peaks (P less than 0.05) and more total GH release (P less than 0.05). This response could not be accounted for by the additive effects of GHRF and somatostatin withdrawal.
生长激素（GH）在体内以脉冲形式分泌。为了解控制这种周期性的信号，我们建立了一种基于灌流的脉冲式GH释放模型。将雄性大鼠垂体前叶分散，并用人类生长激素释放因子-（1-40）（GHRF）脉冲进行灌流，有无持续或间断的生长抑素张力。一项实验包括1小时的基线采集，随后是四个3小时的周期；每个周期包含单次或配对的10分钟3 nM GHRF输注。在测试生长抑素的影响时，方案相同，只是在基线期30分钟时加入0.3 nM生长抑素，然后在整个研究过程中持续或在GHRF输注期间撤去。有生长抑素时的GH基线低于溶剂基线（P<0.05）。GHRF脉冲在200至300 ng·min-1·（10^7个细胞）-1之间产生一致的GH释放峰值，这些峰值不受持续生长抑素的影响。相比之下，在给予GHRF期间撤去生长抑素会引起明显更高的GH峰值（P<0.05）和更多的总GH释放（P<0.05）。这种反应不能用GHRF和撤去生长抑素的累加效应来解释。
