Gatford K L, Fletcher T P, Rao A, Egan A R, Hosking B J, Clarke I J
Department of Agriculture and Resource Management, University of Melbourne, Parkville, Victoria, Australia.
J Endocrinol. 1997 Jan;152(1):19-27. doi: 10.1677/joe.0.1520019.
Factors contributing to sex differences in the somatotrophic axis were investigated in growing lambs. In the first experiment, circulating patterns of GH in venous blood, pituitary content of GH and GH mRNA, and median eminence (ME) contents of GH-releasing factor (GRF) and somatostatin (SRIF) were characterized in prepubertal ram and ewe lambs which were pair-fed to remove sex differences in feed intake. Mean and baseline plasma GH concentrations, GH pulse amplitude, and integrated plasma GH were greater in ram lambs than in ewe lambs, but GH interpulse interval did not differ between sexes. The pituitary GH content and ME contents of GRF and SRIF were greater in rams than in ewes, but steady-state levels of mRNA for GH in the pituitary gland did not differ between sexes. A second experiment investigated sex effects on the levels of SRIF in hypophysial portal blood, and found that these did not differ between sexes. We concluded that the presence of sexually dimorphic patterns of GH secretion in the growing lamb is independent of feed-intake differences between sexes. The lack of sex differences in circulating patterns of SRIF in portal plasma implies that there may be a difference in GRF secretion which may produce sexually dimorphic patterns of GH secretion in lamb.
在生长中的羔羊中研究了导致生长激素轴性别差异的因素。在第一个实验中，对青春期前的公羊和母羊羔羊的静脉血中生长激素（GH）的循环模式、垂体中GH的含量和GH信使核糖核酸（mRNA）以及正中隆起（ME）中生长激素释放因子（GRF）和生长抑素（SRIF）的含量进行了表征，这些羔羊采用配对饲养以消除采食量的性别差异。公羊羔羊的平均和基础血浆GH浓度、GH脉冲幅度以及血浆GH积分均高于母羊羔羊，但两性之间的GH脉冲间期无差异。公羊垂体中的GH含量以及GRF和SRIF的ME含量高于母羊，但垂体中GH mRNA的稳态水平在两性之间无差异。第二个实验研究了性别对垂体门脉血中SRIF水平的影响，发现两性之间无差异。我们得出结论，生长中的羔羊存在GH分泌的性别二态性模式，这与两性之间的采食量差异无关。门脉血浆中SRIF循环模式缺乏性别差异，这意味着GRF分泌可能存在差异，这可能导致羔羊出现GH分泌的性别二态性模式。
