Morgan J B, Wheeler T L, Koohmaraie M, Crouse J D, Savell J W
Department of Animal Science, Texas A&M University, College Station 77843-2471.
J Anim Sci. 1993 Feb;71(2):408-14. doi: 10.2527/1993.712408x.
The effect of castration on endogenous proteinase activity and myofibrillar protein turnover was investigated in cattle. Six each of MARC III composite bulls and steers weighing approximately 210 kg were given ad libitum access to a typical growing diet. At 0, 42, 84, 126, and 168 d, two consecutive 24-h urine samples were obtained. Urine was analyzed for N tau-methylhistidine (N tau MH) and creatinine. Following slaughter after 170 d on feed, a longissimus muscle sample was removed immediately from each carcass for quantification of mu-calpain, m-calpain, calpastatin, cystatin(s), cathepsin B, and cathepsin B + L activities. Bulls were heavier (P < .05) at 126 and 168 d and more efficient (P < .05) in conversion of feed to gain at 84 and 168 d than were steers. Compared with steers, bulls excreted less (P < .05) N tau MH at 84, 126, and 168 d and displayed lower (P < .05) fractional degradation rates (FDR) at all sample times. No differences (P > .05) in calpain or cathepsin activities were observed between bulls and steers. However, muscle from bulls had greater (P < .05) activities of calpastatin and cystatin(s) than that from steers. A negative relationship existed between d-168 FDR and calpastatin (r = -.72; P < .05) and cystatin (r = -.62; P < .05) activities. These results indicate that decreased FDR of skeletal muscle from growing bulls contributes to their greater efficiency of growth and could be related partially to cystatin-mediated cathepsin activity and(or) calpastatin-mediated calpain activity.
研究了去势对牛内源性蛋白酶活性和肌原纤维蛋白周转的影响。选取6头体重约210 kg的MARC III复合公牛和6头阉牛，自由采食典型的生长日粮。在第0、42、84、126和168天，采集连续两个24小时的尿液样本。分析尿液中的N-τ-甲基组氨酸（N-τ-MH）和肌酐。在采食170天后屠宰，立即从每个胴体上取下一块背最长肌样本，用于定量测定μ-钙蛋白酶、m-钙蛋白酶、钙蛋白酶抑制蛋白、胱抑素、组织蛋白酶B以及组织蛋白酶B + L的活性。公牛在第126天和168天体重更重（P < 0.05），在第84天和168天饲料转化为增重的效率更高（P < 0.05）。与阉牛相比，公牛在第84、126和168天排出的N-τ-MH较少（P < 0.05），并且在所有采样时间的降解率（FDR）较低（P < 0.05）。公牛和阉牛之间在钙蛋白酶或组织蛋白酶活性上未观察到差异（P > 0.05）。然而，公牛肌肉中的钙蛋白酶抑制蛋白和胱抑素活性比阉牛更高（P < 0.05）。第168天的FDR与钙蛋白酶抑制蛋白（r = -0.72；P < 0.05）和胱抑素（r = -0.62；P < 0.05）活性之间存在负相关。这些结果表明，生长公牛骨骼肌FDR的降低有助于其更高的生长效率，并且可能部分与胱抑素介导的组织蛋白酶活性和（或）钙蛋白酶抑制蛋白介导的钙蛋白酶活性有关。
