Eisemann J H, Huntington G B, Ferrell C L
USDA-ARS, Roman L. Hruska U.S. Meat Animal Research Center, Clay Center, NE 68933.
J Anim Sci. 1988 Feb;66(2):342-53. doi: 10.2527/jas1988.662342x.
The objective of this study was to measure acute (d 1) and chronic (d 9) effects of dietary clenbuterol on heart rate, blood flow, oxygen uptake, and net uptake/release of metabolites in the hindquarters of growing steers. The design was a single reversal with two 9-d periods of control or 8 mg clenbuterol/d with 5 d between periods. Within 2 h of initial consumption of 2 mg clenbuterol (d 1), heart rate and blood flow doubled and arterial plasma concentrations of glucose, L-lactate and nonesterified fatty acid (NEFA) increased, whereas alpha-NH2 N and NH3 concentrations decreased, demonstrating an acute response. Uptake of oxygen increased and net uptake of alpha-NH2 N decreased. Net release of both L-lactate and NEFA increased. On d 9, there were no acute responses to clenbuterol consumption; however, heart rate, blood flow, and NEFA concentration remained chronically elevated, and plasma concentrations of acetate and propionate decreased compared with control feeding. Net uptake of alpha-NH2 N, oxygen and release of L-lactate by the hindquarters chronically increased on d 9 of clenbuterol feeding. Changes in both blood flow and arteriovenous (AV) concentration difference contributed to changes in uptake/release. The chronic metabolic changes and oxygen uptake were consistent with increased N retention in the hindquarters through increased protein synthesis, decreased use of acetate and increased reliance on NEFA for cellular energy. In conclusion, the data show that the perturbation of homeostatic regulation by dietary clenbuterol on d 1 evolved to establishment of homeorhetic regulation by d 9 that is consistent with increased skeletal protein accretion in growing steers.
本研究的目的是测定日粮中克伦特罗对生长育肥牛后躯心率、血流量、氧气摄取以及代谢物净摄取/释放的急性（第1天）和慢性（第9天）影响。试验设计为单次反转试验，包括两个9天的对照期或每天8毫克克伦特罗饲喂期，两期之间间隔5天。在初次摄入2毫克克伦特罗（第1天）后2小时内，心率和血流量增加了一倍，动脉血浆中葡萄糖、L-乳酸和非酯化脂肪酸（NEFA）浓度升高，而α-NH2 N和NH3浓度降低，表明出现了急性反应。氧气摄取增加，α-NH2 N净摄取减少。L-乳酸和NEFA的净释放均增加。在第9天，对克伦特罗摄入未出现急性反应；然而，心率、血流量和NEFA浓度持续升高，与对照饲喂相比，血浆中乙酸盐和丙酸盐浓度降低。在克伦特罗饲喂的第9天，后躯对α-NH2 N、氧气的净摄取以及L-乳酸的释放长期增加。血流量和动静脉（AV）浓度差的变化均导致了摄取/释放的变化。慢性代谢变化和氧气摄取与后躯通过增加蛋白质合成、减少乙酸盐利用以及增加对NEFA作为细胞能量的依赖而导致的氮保留增加相一致。总之，数据表明，日粮中克伦特罗在第1天对稳态调节的干扰在第9天演变为建立同功调节，这与生长育肥牛骨骼蛋白质积累增加相一致。
