Miller M F, Garcia D K, Coleman M E, Ekeren P A, Lunt D K, Wagner K A, Procknor M, Welsh T H, Smith S B
Dept. of Anim. Sci., Texas A&M University, College Station 77843.
J Anim Sci. 1988 Jan;66(1):12-20. doi: 10.2527/jas1988.66112x.
The present study was conducted to determine the effects of feeding clenbuterol on adipose tissue and longissimus muscle growth in heifers. For 50 d, 14 heifers were fed either a sucrose-based, clenbuterol supplement or a placebo in which the clenbuterol had been omitted. The heifers were slaughtered in two groups, based on initial weight. Adipose tissue from several anatomical sites and longissimus muscle (depending on slaughter group) were obtained fresh at slaughter. Changes in carcass characteristics elicited by clenbuterol were similar to those reported by others for steers and sheep. Subcutaneous (sc) and intramuscular (im), but not perirenal, adipocytes were smaller and there were more cells per g tissue in the adipose tissue depots of the clenbuterol-fed heifers. Clenbuterol decreased lipogenic enzyme activities, fatty acid-binding protein activity, basal lipolysis and acetate incorporation into glyceride-fatty acids (P less than .05) in sc adipose tissue, but had no effect (P greater than .05) on lipogenesis or lipolysis in im adipose tissue. Clenbuterol elicited a 20% increase in type II myofiber diameters (P less than .05) but had no effect on type I myofiber diameters. In vitro growth hormone release by perifused anterior pituitaries was not affected significantly by long-term in vivo exposure to clenbuterol. These data indicate that a depression in lipogenesis is the mechanism by which clenbuterol decreases subcutaneous fat accretion in cattle.
本研究旨在确定饲喂克伦特罗对小母牛脂肪组织和背最长肌生长的影响。在50天的时间里，14头小母牛被分别饲喂添加了克伦特罗的蔗糖基饲料或不含克伦特罗的安慰剂。根据初始体重，小母牛被分成两组屠宰。在屠宰时，从几个解剖部位获取新鲜的脂肪组织和背最长肌（取决于屠宰组）。克伦特罗引起的胴体特征变化与其他关于公牛和绵羊的报道相似。饲喂克伦特罗的小母牛脂肪组织库中，皮下和肌内脂肪细胞变小，每克组织中的细胞数量增多，但肾周脂肪细胞无此变化。克伦特罗降低了皮下脂肪组织中脂肪生成酶活性、脂肪酸结合蛋白活性、基础脂肪分解以及乙酸掺入甘油脂肪酸的比例（P<0.05），但对肌内脂肪组织的脂肪生成或脂肪分解没有影响（P>0.05）。克伦特罗使II型肌纤维直径增加了20%（P<0.05），但对I型肌纤维直径没有影响。长期体内暴露于克伦特罗对灌流垂体前叶体外生长激素释放没有显著影响。这些数据表明，脂肪生成减少是克伦特罗降低牛皮下脂肪沉积的机制。
