Hannon K, Gronowski A, Trenkle A
Department of Animal Science, Iowa State University, Ames 50011.
Proc Soc Exp Biol Med. 1991 Feb;196(2):155-63. doi: 10.3181/00379727-196-43172.
Growth hormone (GH), insulin-like growth factor-1 (IGF-1), and thyroid hormone (T3 and T4) concentrations in blood plasma of 18 crossbred cattle (six bulls, six steers, and six heifers) were measured over an 8-hr period. One week later at slaughter, IGF-1 production by liver slices and IGF-1 mRNA concentrations in skeletal muscle and liver were measured. Bulls had higher (P less than 0.05) mean plasma GH and GH peak amplitudes (P less than 0.01) than heifers, and values for steers were intermediate between bulls and heifers. Baseline GH concentrations and number of GH peaks were not significantly different for the three groups. Bulls had 1.6-fold (P less than 0.01) and 3.0-fold (P less than 0.01) greater liver IGF-1 mRNA concentrations than steers or heifers, respectively, whereas the steers had 1.8-fold (P less than 0.05) greater IGF-1 mRNA in liver than heifers. Production of IGF-1 by liver slices was greater (P less than 0.05) in bulls than steers or heifers. Bulls had 1.3-fold greater plasma IGF-1 than steers (P less than 0.01), whereas steers had 1.8-fold greater plasma IGF-1 than heifers (P less than 0.01). There were no significant differences in concentrations of skeletal muscle IGF-1 mRNA between the three groups of animals. Liver IGF-1 mRNA, liver IGF-1 production, and plasma IGF-1 were all significantly correlated with gain and mean GH peak amplitude, but not with GH baseline, GH peak frequency, or concentrations of T3 and T4. Concentrations if IGF-1 mRNA in skeletal muscle were not correlated to gain or any parameter of the GH profile. Plasma concentrations of T3 were significantly (P less than 0.05) negatively correlated to plasma GH baseline concentrations. Muscle IGF-1 mRNA concentration was negatively related to plasma T4 and T3. The results of this study suggest that the cascade of events starting with secretion of GH from the pituitary, expression of liver IGF-1 mRNA, and secretion of IGF-1 by the liver are important phenomena for growth of cattle.
在8小时内测定了18头杂交牛（6头公牛、6头阉牛和6头小母牛）血浆中生长激素（GH）、胰岛素样生长因子-1（IGF-1）和甲状腺激素（T3和T4）的浓度。一周后屠宰时，测定了肝切片的IGF-1产量以及骨骼肌和肝脏中IGF-1 mRNA的浓度。公牛的平均血浆GH和GH峰值幅度高于小母牛（P<0.05），且差异极显著（P<0.01），阉牛的值介于公牛和小母牛之间。三组动物的GH基础浓度和GH峰值数量无显著差异。公牛肝脏中IGF-1 mRNA浓度分别比阉牛和小母牛高1.6倍（P<0.01）和3.0倍（P<0.01），而阉牛肝脏中IGF-1 mRNA浓度比小母牛高1.8倍（P<0.05）。公牛肝切片产生的IGF-1比阉牛或小母牛多（P<0.05）。公牛的血浆IGF-1比阉牛高1.3倍（P<0.01），而阉牛的血浆IGF-1比小母牛高1.8倍（P<0.01）。三组动物骨骼肌中IGF-1 mRNA浓度无显著差异。肝脏IGF-1 mRNA、肝脏IGF-1产量和血浆IGF-1均与增重和平均GH峰值幅度显著相关，但与GH基础值、GH峰值频率或T3和T4浓度无关。骨骼肌中IGF-1 mRNA浓度与增重或GH谱的任何参数均无相关性。血浆T3浓度与血浆GH基础浓度呈显著负相关（P<0.05）。肌肉IGF-1 mRNA浓度与血浆T4和T3呈负相关。本研究结果表明，从垂体分泌GH开始，到肝脏表达IGF-1 mRNA，再到肝脏分泌IGF-1这一系列事件，对于牛的生长来说是重要现象。
