Gootwine E, Suttie J M, McEwan J C, Veenvliet B A, Littlejohn R P, Fennessy P F, Montgomery G W
Institute of Animal Science, ARO, Volcani Center, Bet Dagan, Israel.
Domest Anim Endocrinol. 1997 Nov;14(6):381-90. doi: 10.1016/s0739-7240(98)00043-5.
The effects of natural variation in the number of copies of the growth hormone (GH) gene on growth parameters, plasma GH profiles, and the response to GHRH challenge were compared in Coopworth ram lambs from selection lines differing in body composition and GH levels. Different genotypes at the GH locus carried two, three, or four copies of the GH gene and GH secretion was studied under ad libitum feeding conditions and in the fasted state. There were no significant effects of GH genotype on any parameters of growth or body composition. Basal serum GH concentration, GH pulse frequency, and GH pulse amplitude differed significantly with selection line and fasting, but did not differ significantly between the GH genotypes. Significant differences of subtle nature were found between the GH genotypes in their responsiveness to GHRH. For the ad libitum-fed Lean selection line animals, the first GHRH challenge resulted in a higher mean maximum response for GH1/GH1 than GH2/GH2 (P < 0.05). Between the first and the second challenges there was a decrease in maximum response for the GH1/GH1 genotype and an increase for the GH2/GH2 genotype (P < 0.05 for GH genotype main effect). The differences between GH genotypes in response to GHRH challenge suggest that polymorphism in the number of GH gene copies in sheep may have physiological implications for the function of the GH axis, which may be manifested in growing lambs only under specific genotype-environment combinations.
在体组成和生长激素（GH）水平不同的选择系库泊华斯公羔羊中，比较了生长激素（GH）基因拷贝数自然变异对生长参数、血浆GH谱以及对生长激素释放激素（GHRH）刺激反应的影响。GH基因座上的不同基因型携带两个、三个或四个GH基因拷贝，并在自由采食条件和禁食状态下研究了GH分泌情况。GH基因型对任何生长或体组成参数均无显著影响。基础血清GH浓度、GH脉冲频率和GH脉冲幅度因选择系和禁食情况而有显著差异，但在GH基因型之间无显著差异。在对GHRH的反应性方面，GH基因型之间存在细微但显著的差异。对于自由采食的瘦型选择系动物，首次GHRH刺激导致GH1/GH1基因型的平均最大反应高于GH2/GH2基因型（P<0.05）。在首次和第二次刺激之间，GH1/GH1基因型的最大反应下降，而GH2/GH2基因型的最大反应增加（GH基因型主效应P<0.05）。GH基因型对GHRH刺激反应的差异表明，绵羊GH基因拷贝数的多态性可能对GH轴的功能具有生理影响，这种影响可能仅在特定的基因型-环境组合下在生长羔羊中表现出来。
