Dahl G E, Chapin L T, Moseley W M, Kamdar M B, Tucker H A
Department of Animal Science, Michigan State University, East Lansing 48824.
J Dairy Sci. 1994 Sep;77(9):2518-25. doi: 10.3168/jds.s0022-0302(94)77193-9.
Two experiments were conducted to determine the galactopoietic effects of an analog of growth hormone-releasing factor. Specific replacements were made in the AA sequence of growth hormone-releasing factor to produce a growth hormone-releasing factor analog with enhanced stability in vivo. In Experiment 1, 24 Holstein cows were infused i.v. with 0, .33, 1, or 3 mg/d of growth hormone-releasing factor analog for 20 d. Infusion of the analog increased mean serum concentrations of somatotropin, IGF-I, and NEFA. The analog also increased milk yield as much as 44% relative to that of controls. In Experiment 2, 24 Holstein cows were infused i.v. with 0, .11, .33, or 1 mg/d of analog for 60 d. Infusion of analog increased serum concentrations of somatotropin, IGF-I, and NEFA in a dose-dependent manner. At 1 mg/d, the analog increased SCM yield 28% throughout the infusion period relative to the 0 mg/d controls. In summary, a growth hormone-releasing factor analog increased milk yield and serum concentrations of somatotropin and IGF-I. Furthermore, this galactopoietic activity was mediated through the somatotropic axis.
进行了两项实验以确定生长激素释放因子类似物的催乳作用。在生长激素释放因子的氨基酸序列中进行了特定替换，以产生一种在体内具有增强稳定性的生长激素释放因子类似物。在实验1中，对24头荷斯坦奶牛静脉注射0、0.33、1或3毫克/天的生长激素释放因子类似物，持续20天。注射该类似物可提高生长激素、胰岛素样生长因子-I和非酯化脂肪酸的平均血清浓度。与对照组相比，该类似物还使产奶量提高了44%。在实验2中，对24头荷斯坦奶牛静脉注射0、0.11、0.33或1毫克/天的类似物，持续60天。注射类似物可使生长激素、胰岛素样生长因子-I和非酯化脂肪酸的血清浓度呈剂量依赖性增加。在1毫克/天的剂量下，与0毫克/天的对照组相比，该类似物在整个注射期间使标准乳产量提高了28%。总之，生长激素释放因子类似物提高了产奶量以及生长激素和胰岛素样生长因子-I的血清浓度。此外，这种催乳活性是通过生长激素轴介导的。
