Hayden J M, Bergen W G, Merkel R A
Department of Animal Science, Michigan State University, East Lansing 48824.
J Anim Sci. 1992 Jul;70(7):2109-19. doi: 10.2527/1992.7072109x.
Skeletal muscle protein degradation, measured by urinary N tau-methylhistidine excretion, and circulating concentrations of growth hormone (GH), insulin (INS), and cortisol (CT) were monitored in steers before and after implantation with estradiol-17 beta (E2; 24 mg) and trenbolone acetate (TBA; 300 mg). Yearling crossbred steers (n = 43) were randomly assigned to four treatment groups in a 2 x 2 factorial arrangement: nonimplanted controls (C); TBA; E2; and TBA plus E2 (TBA+E2). A subgroup (Block 1) of 16 steers was bled on d -12, 31, and 72 after implanting. Deposition of skeletal muscle protein was markedly increased (P less than .001) by E2 and TBA+E2 treatment. This response occurred mainly within the first 40 d after implantation and declined (P less than .001) in concert with decreasing (P less than .01) concentration of serum E2. Anabolic steroid treatment did not affect the rate of skeletal muscle protein breakdown. There was no apparent relationship between reduced serum CT concentration (linear effect; P less than .01) in TBA-treated steers and skeletal muscle protein degradation rate. Blood concentration and pulse activity of INS were not affected by anabolic steroid administration. Both TBA- and TBA+E2-implanted steers displayed a linear decrease (P less than .05) in serum GH concentration over time, which was similar to C. Lowered mean GH concentration resulted from a reduction (TBA main effect; P less than .05) in pulse amplitude of GH. Unlike TBA, TBA+E2, and C, only E2 maintained serum GH concentrations over time. Although increased muscle protein deposition was evident in TBA+E2-treated steers, an obvious causal relationship between this response and circulating GH, INS, and CT was not revealed. These results do not support the concept that combined androgenic agent and estrogen administration effectively reduce bovine muscle protein degradation by static modulation of circulating endogenous anabolic and antianabolic hormones.
通过尿中N-τ-甲基组氨酸排泄量来测定骨骼肌蛋白降解，并监测了在植入17β-雌二醇（E2；24毫克）和醋酸群勃龙（TBA；300毫克）前后阉牛体内生长激素（GH）、胰岛素（INS）和皮质醇（CT）的循环浓度。将一岁杂交阉牛（n = 43）按照2×2析因设计随机分为四个处理组：未植入对照组（C）；TBA组；E2组；以及TBA + E2组。在植入后的第 -12、31和72天，对16头阉牛的一个亚组（第1组）进行采血。E2和TBA + E2处理显著增加了骨骼肌蛋白沉积（P <.001）。这种反应主要发生在植入后的前40天内，并随着血清E2浓度的降低（P <.01）而下降（P <.001）。合成代谢类固醇处理不影响骨骼肌蛋白分解速率。在TBA处理的阉牛中，血清CT浓度降低（线性效应；P <.01）与骨骼肌蛋白降解速率之间没有明显关系。合成代谢类固醇给药不影响INS的血药浓度和脉冲活性。随着时间的推移，TBA和TBA + E2植入的阉牛血清GH浓度均呈线性下降（P <.05），这与C组相似。GH平均浓度降低是由于GH脉冲幅度降低（TBA主效应；P <.05）所致。与TBA、TBA + E2和C组不同，只有E2能随时间维持血清GH浓度。尽管在TBA + E2处理的阉牛中肌肉蛋白沉积增加明显，但未揭示这种反应与循环中的GH、INS和CT之间存在明显的因果关系。这些结果不支持联合使用雄激素制剂和雌激素通过静态调节循环内源性合成代谢和抗合成代谢激素来有效降低牛肌肉蛋白降解的概念。
