Geris K L, Hickey G J, Vanderghote A, Kühn E R, Darras V M
Laboratory of Comparative Endocrinology, Leuven, Belgium.
Endocrine. 2001 Feb;14(1):67-72. doi: 10.1385/ENDO:14:1:067.
In the chicken growth hormone (GH) secretion is predominantly controlled by two hormones, thyrotropin-releasing hormone (TRH) and somatostatin (SRIH), respectively stimulating and inhibiting GH release. In view of the hypothesis of a novel GH secretagogue (GHS) in mammals, this specific species was used to further assess the exact function of two nonpeptidyl GHSs-L-692,429 and L-163,255. Both synthetic products stimulate GH secretion directly at the level of the pituitary as shown in in vitro perifusion studies. Plasma GH levels increase within 10-15 min after a single challenge of L-692,429 or L-163,255. A SRIH pretreatment dimishes this GH response. Both GH-releasing peptide mimetics decrease hypothalamic TRH concentrations, whereas SRIH levels are not affected. The novel GHS may therefore control GH secretion both at the level of the pituitary and the hypothalamus. The present article shows that nonpeptidyl mimetics also control GH secretion in nonmammalian species suggesting that the endogenous hormone may be a conserved GH stimulator in several vertebrates. The GH response to GHS in birds may be regulated both directly at the level of the pituitary and by releasing another endogenous GH stimulator (TRH) from the hypothalamus.
在鸡体内，生长激素（GH）的分泌主要受两种激素控制，即促甲状腺激素释放激素（TRH）和生长抑素（SRIH），它们分别刺激和抑制GH的释放。鉴于哺乳动物中存在新型生长激素促分泌素（GHS）的假说，利用这种特定物种来进一步评估两种非肽类GHS——L-692,429和L-163,255的确切功能。如体外灌流研究所示，这两种合成产物均能在垂体水平直接刺激GH分泌。单次给予L-692,429或L-163,255后，血浆GH水平在10 - 15分钟内升高。预先给予SRIH可减弱这种GH反应。两种生长激素释放肽模拟物均降低下丘脑TRH浓度，而SRIH水平不受影响。因此，这种新型GHS可能在垂体和下丘脑水平均控制GH分泌。本文表明，非肽类模拟物在非哺乳动物物种中也能控制GH分泌，这表明内源性激素可能是几种脊椎动物中保守的GH刺激物。鸟类对GHS的GH反应可能在垂体水平直接受到调节，也可能通过从下丘脑释放另一种内源性GH刺激物（TRH）来调节。
