Byrem T M, Beermann D H, Robinson T F
Department of Animal Science, Cornell University, Ithaca, NY 14853, USA.
J Anim Sci. 1996 Dec;74(12):2907-16. doi: 10.2527/1996.74122907x.
Dose-dependent effects of cimaterol (CIM) on hindlimb metabolism were determined in six steers (247 +/- 22 kg BW) using a close arterial infusion. The external iliac vessels of both hindlimbs were catheterized to accommodate measurement of blood flow, circulating concentrations, and net flux of NEFA, lactate, and alpha-amino nitrogen (AAN) during infusion of CIM at 0, .05, .1, .3, .7, 1 and 3 micrograms/ min. Close arterial infusion of CIM in the hindlimb of steers can be used to achieve a local concentration elevation that is required to differentiate local and systemic effects in vivo. Calculated plasma threshold CIM concentration required to initiate cardiovascular responses was 21 pg/mL, which resulted from an infusion rate of .3 microgram/min. Threshold concentrations of CIM for stimulation of NEFA and lactate net flux in the hindlimb were 38 and 34 pg/mL, respectively, and would be achieved with an infusion rate of .7 microgram/min. All measured responses except AAN net flux exhibited significant linear and quadratic dose effects, and responses in the treated hindlimb were always severalfold greater than in the contralateral control hindlimb. Maximal differences between treated and control hindlimb blood flow occurred with a CIM infusion rate of .7 microgram/min, but the highest infusion rate (3 micrograms/min) was required to maximize differences in NEFA and lactate flux. Therefore, to minimize cardiovascular and other systemic responses and optimize direct hindlimb responses, an infusion rate of .5 microgram of CIM/ min should cause significant stimulation of beta-adrenergic receptors only in the CIM-infused hindlimb of young, growing steers.
使用动脉近端输注法，在6头体重247±22千克的阉牛中测定了西马特罗（CIM）对后肢代谢的剂量依赖性效应。在以0、0.05、0.1、0.3、0.7、1和3微克/分钟的速率输注CIM期间，将两侧后肢的髂外血管插入导管，以测量血流、循环浓度以及非酯化脂肪酸（NEFA）、乳酸和α-氨基氮（AAN）的净通量。在阉牛后肢进行动脉近端输注CIM可用于实现局部浓度升高，这是区分体内局部和全身效应所必需的。引发心血管反应所需的计算血浆阈值CIM浓度为21皮克/毫升，这是由0.3微克/分钟的输注速率产生的。刺激后肢NEFA和乳酸净通量的CIM阈值浓度分别为38和34皮克/毫升，以0.7微克/分钟的输注速率可达到该浓度。除AAN净通量外，所有测量的反应均表现出显著的线性和二次剂量效应，并且处理后肢的反应总是比对侧对照后肢大几倍。当CIM输注速率为0.7微克/分钟时，处理后肢与对照后肢的血流差异最大，但需要最高输注速率（3微克/分钟）才能使NEFA和乳酸通量的差异最大化。因此，为了使心血管和其他全身反应最小化并优化直接后肢反应，对于年轻的生长阉牛，0.5微克CIM/分钟的输注速率应仅在输注CIM的后肢中引起β-肾上腺素能受体的显著刺激。
