Speck P A, Collingwood K M, Bardsley R G, Tucker G A, Gilmour R S, Buttery P J
Department of Applied Biochemistry and Food Science, University of Nottingham Faculty of Agricultural and Food Science, Loughborough, Leicestershire, UK.
Biochimie. 1993;75(10):917-23. doi: 10.1016/0300-9084(93)90049-x.
Prolonged dietary inclusion of beta-adrenergic agonists can induce skeletal muscle hypertrophy in meat animals, by a mechanism probably related to the calcium-dependent proteolytic enzymes, or calpains, and in particular to their specific inhibitor calpastatin. Calpain and calpastatin activities are also believed to be important factors during post-mortem tenderisation of meat. beta-Agonist treatment is generally associated with increased calpastatin activity, which may lead to meat toughness. The aim of the present study was to examine the effect of a short period of cimaterol (feeding for 8 days, followed by reversion to a normal diet for a further 24 days) on muscle growth and on calpain isoform and calpastatin activities and specific mRNA abundance in the longissimus dorsi (LD) muscle. Significant changes were detected in LD wet weight and in calpastatin activity and mRNA after only 8 days treatment with cimaterol. After 24 further days on a control diet, both LD wet weight and calpastatin activity were not significantly different (P > 0.05) from untreated controls of the same age, although calpastatin mRNA stayed surprisingly high. In contrast to several earlier studies, changes in calpain I (or mu-calpain) and calpain II (or m-calpain) activity and calpain I mRNA were not significantly different (P > 0.05) from controls in any groups. These data suggest that calpastatin activity rather than the activity of either calpain isoform is closely linked to beta-agonist-induced muscle hypertrophy. Changes in calpastatin mRNA are not directly proportional to inhibitory activity, suggesting that variable mRNA species may be transcribed, spliced or stabilised, but not necessarily translated as part of the beta-agonist response.
长期在日粮中添加β-肾上腺素能激动剂可诱导肉用动物骨骼肌肥大，其机制可能与钙依赖性蛋白水解酶即钙蛋白酶有关，尤其与其特异性抑制剂钙蛋白酶抑制蛋白有关。钙蛋白酶和钙蛋白酶抑制蛋白的活性也被认为是宰后肉嫩化过程中的重要因素。β-激动剂处理通常与钙蛋白酶抑制蛋白活性增加有关，这可能导致肉变坚韧。本研究的目的是检测短期西马特罗处理（饲喂8天，然后恢复正常日粮24天）对背最长肌（LD）肌肉生长、钙蛋白酶同工型、钙蛋白酶抑制蛋白活性及特异性mRNA丰度的影响。在用西马特罗处理仅8天后，就检测到LD湿重、钙蛋白酶抑制蛋白活性及mRNA有显著变化。在继续饲喂对照日粮24天后，尽管钙蛋白酶抑制蛋白mRNA仍出人意料地高，但LD湿重和钙蛋白酶抑制蛋白活性与同龄未处理对照相比无显著差异（P>0.05）。与早期的几项研究不同，任何组中钙蛋白酶I（或μ-钙蛋白酶）和钙蛋白酶II（或m-钙蛋白酶）活性及钙蛋白酶I mRNA的变化与对照相比均无显著差异（P>0.05）。这些数据表明，与β-激动剂诱导的肌肉肥大密切相关的是钙蛋白酶抑制蛋白活性而非任何一种钙蛋白酶同工型的活性。钙蛋白酶抑制蛋白mRNA的变化与抑制活性并非直接成比例，这表明可能转录、剪接或稳定了可变的mRNA种类，但不一定作为β-激动剂反应的一部分进行翻译。
