Trout W E, Schanbacher B D
U.S. Department of Agriculture, Roman L. Hruska U.S. Meat Animal Research Center, Nebraska 68933.
J Endocrinol. 1990 Apr;125(1):123-9. doi: 10.1677/joe.0.1250123.
Steers were actively immunized at 81 days of age against human serum albumin (hSA; controls) or hSA conjugated to either somatostatin (SRIF) or growth hormone-releasing factor (GRF). Binding titres were observed for the respective peptide antigens after all steers had been given booster immunizations. Although no effects of treatment were observed in SRIF-immunized steers, mean serum concentrations of GH and insulin-like growth factor (IGF-I) were suppressed (P less than 0.01) in GRF-immunized steers when compared with hSA-immunized controls. Mean concentrations of prolactin did not differ with treatment but showed seasonal fluctuations (P less than 0.001) associated with changes in the daylength. In contrast to its marked effect upon serum concentrations of IGF-I, immunization against GRF resulted in a relatively small (6%) but significant decrease in body weight gain (P less than 0.01) and an increase in carcass backfat thickness (P less than 0.05). In summary, our findings have shown the susceptibility of steers to growth modulation by GRF immunoneutralization. Secondly, the poor relationship observed between serum concentrations of IGF-I and growth rates in GRF-immunized steers suggested that circulating IGF-I may not be the principle factor determining the post-weaning growth rate in cattle.
在81日龄时，对肉牛进行主动免疫，使其针对人血清白蛋白（hSA；对照组）或与人生长抑素（SRIF）或生长激素释放因子（GRF）偶联的hSA。在所有肉牛接受加强免疫后，观察各自肽抗原的结合滴度。虽然在接受SRIF免疫的肉牛中未观察到处理效果，但与接受hSA免疫的对照组相比，接受GRF免疫的肉牛中生长激素（GH）和胰岛素样生长因子（IGF-I）的平均血清浓度受到抑制（P<0.01）。催乳素的平均浓度在不同处理间无差异，但呈现出与日照长度变化相关的季节性波动（P<0.001）。与对IGF-I血清浓度的显著影响相反，针对GRF的免疫导致体重增加相对小幅下降（6%）但显著（P<0.01），且胴体背膘厚度增加（P<0.05）。总之，我们的研究结果表明肉牛对GRF免疫中和引起的生长调节敏感。其次，在接受GRF免疫的肉牛中观察到的IGF-I血清浓度与生长速率之间的不良关系表明，循环中的IGF-I可能不是决定犊牛断奶后生长速率的主要因素。
