Stanko R L, Armstrong J D, Cohick W S, Harvey R W, Simpson R B, Hartnell G F, Heimer E P, Campbell R M
Department of Animal Science, North Carolina State University, Raleigh 27695-7621.
J Anim Sci. 1994 Jul;72(7):1786-95. doi: 10.2527/1994.7271786x.
Two experiments examined whether replacement therapy with recombinantly derived bovine somatotropin (rbST) would induce puberty in heifers that had been actively immunized at 6 mo of age against growth hormone-releasing factor (GRF). Heifers received daily i.m. injections of 25 mg of rbST (Exp. 1, n = 6; Exp. 2, n = 4) or vehicle (VEH; Exp. 1, n = 6; Exp. 2, n = 4) for 56 d. Serum concentrations of somatotropin (ST, nanograms/milliter) were low in all heifers before first injection in Exp. 1 (1.56 +/- .04) and 2 (.95 +/- .03). During treatment, serum ST was greater (P < .01) in rbST than in VEH heifers (75.4 +/- 4.8 vs 2.8 +/- .1 ng/mL, respectively) in both experiments and remained increased through d 57 (32.2 +/- 6.4 vs .90 +/- .01 ng/mL). IN Exp. 1 and 2, concentrations of serum IGF-I were similar in rbST and VEH heifers before treatment, increased (P < .01) 12 h after first rbST, and remained increased (P < .01) through d 57 in rbST heifers. Concentrations of serum insulin (INS) and plasma glucose (GLU) were similar (P > .10) in rbST and VEH heifers before first injection (Exp. 1 and 2). Serum INS (micro-units/milliliter) was greater (P < .01) in rbST (61.7 +/- 3.7 and 36.0 +/- 2.4) than in VEH (12.4 +/- 1.6 and 8.1 +/- 1.0) heifers on d 1 or 2 only, in Exp. 1 and 2, respectively. In Exp. 1, GLU was increased (P < .05) by rbST on d 2 through 57, but only on d 1 in Exp. 2. Proportion of heifers pubertal by d 21 tended to be greater (P < .07) in rbST (3 of 6) than in VEH (0 of 5) heifers in Exp. 1, but not in Exp. 2 (1 of 4 vs 1 of 4, respectively). All heifers in Exp. 1 and 50% of the heifers in Exp. 2 attained puberty by d 56. Daily rbST increased ST, IGF-I, INS, and GLU but did not hasten onset of puberty in heifers immunized against GRF.
两项实验研究了用重组牛生长激素（rbST）替代疗法是否会使6月龄时主动免疫生长激素释放因子（GRF）的小母牛进入青春期。小母牛每天肌肉注射25毫克rbST（实验1，n = 6；实验2，n = 4）或赋形剂（VEH；实验1，n = 6；实验2，n = 4），持续56天。在实验1（1.56±0.04）和实验2（0.95±0.03）中，首次注射前所有小母牛的血清生长激素（ST，纳克/毫升）浓度都很低。在治疗期间，两个实验中rbST组小母牛的血清ST均高于（P < 0.01）VEH组小母牛（分别为75.4±4.8与2.8±0.1纳克/毫升），并且在第57天一直保持升高（32.2±6.4与0.90±0.01纳克/毫升）。在实验1和实验2中，rbST组和VEH组小母牛治疗前血清IGF-I浓度相似，首次注射rbST后12小时升高（P < 0.01），并且在rbST组小母牛中直到第57天一直保持升高（P < 0.01）。首次注射前（实验1和实验2），rbST组和VEH组小母牛的血清胰岛素（INS）和血浆葡萄糖（GLU）浓度相似（P > 0.10）。仅在实验1和实验2的第1天或第2天，rbST组小母牛的血清INS（微单位/毫升）高于（P < 0.01）VEH组小母牛（分别为61.7±3.7和36.0±2.4与12.4±1.6和8.1±1.0）。在实验1中，rbST使GLU在第2天至57天升高（P < 0.05），但在实验2中仅在第1天升高。在实验1中，到第21天进入青春期的小母牛比例，rbST组（6头中的3头）比VEH组（5头中的0头）趋于更高（P < 0.07），但在实验2中并非如此（分别为4头中的1头与4头中的1头）。实验1中的所有小母牛以及实验2中50%的小母牛在第56天进入青春期。每日注射rbST可提高ST、IGF-I、INS和GLU，但并未加速免疫GRF的小母牛青春期的开始。
