Young O A, Foote D M, Bass J J
Meat Industry Research Institute of New Zealand (Inc.), PO Box 617, Hamilton, New Zealand.
Meat Sci. 1986;16(3):189-97. doi: 10.1016/0309-1740(86)90025-2.
Two trials are reported in which bulls were implanted with zeranol and slaughtered at 18 months. There was no significant change in carcass weight due to zeranol in either trial. Samples of the longissimus dorsi (LD) and splenius (Sp) were cross-cryosectioned, stained for myofibrillar ATPase and examined by conventional light microscopy. The stain resolved three fibre types: I, slow contracting with an oxidative metabolism, IIA, fast-oxidative-glycolytic and IIB, fast-glycolytic. In the LD from treated bulls, the occurrence of IIB fibres was increased, apparently at the expense of IIA fibres, as the occurrence of I fibres was unchanged. These occurrence changes parallelled previously reported effects of castration. Changes in Sp were less dramatic. In one trial IIB fibres were absent from all Sp muscles, but, in the other, some of the Sp muscles from treated animals contained these fibres whereas they were absent from the Sp of the control group. If the changes in fibre type occurrence due to zeranol extend to skeletal muscles other than LD and Sp, there is likely to be a subtle change in the musculature's metabolism. Fibre areas were largely unaffected by zeranol. In this respect zeranol did not mimic castration.
报道了两项试验，在试验中给公牛植入玉米赤霉醇，并在18个月时屠宰。在两项试验中，玉米赤霉醇均未使胴体重量发生显著变化。采集背最长肌（LD）和夹肌（Sp）样本进行交叉冷冻切片，用肌原纤维ATP酶染色，并通过传统光学显微镜检查。染色分辨出三种纤维类型：I型，收缩缓慢，具有氧化代谢；IIA型，快速氧化糖酵解型；IIB型，快速糖酵解型。在接受处理的公牛的背最长肌中，IIB型纤维的比例增加，显然是以IIA型纤维为代价，因为I型纤维的比例未变。这些比例变化与先前报道的去势效果相似。夹肌的变化不那么显著。在一项试验中，所有夹肌中均不存在IIB型纤维，但在另一项试验中，接受处理动物的一些夹肌中含有这些纤维，而对照组的夹肌中则没有。如果玉米赤霉醇引起的纤维类型比例变化扩展到背最长肌和夹肌以外的骨骼肌，肌肉组织的代谢可能会发生细微变化。纤维面积在很大程度上不受玉米赤霉醇的影响。在这方面，玉米赤霉醇与去势不同。
