Acute responses of muscle protein metabolism to reduced blood flow reflect metabolic priorities for homeostasis.
Acute responses of muscle protein metabolism to reduced blood flow reflect metabolic priorities for homeostasis.
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肌肉蛋白质代谢对血流量减少的急性反应反映了体内平衡的代谢优先级。
DOI：
10.1152/ajpendo.00467.2007
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
Wolfe,RobertR
中科院分区：
文献类型：
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作者：
Zhang,Xiao-Jun;Irtun,Oivind;Chinkes,DavidL;Wolfe,RobertR
本实验采用静脉注射法、示踪剂掺入法和示踪剂释放法，以1-[ring-13 C6]苯丙氨酸为示踪剂，测定家兔后肢肌肉蛋白质合成和分解的动力学。分别采用超声流量计法、染料稀释法和微球法测定股动脉、腿部和肌肉毛细血管中的流速。股动脉血流量占下肢血流量的65%。股动脉血流量减少50%，腿部血流量减少28%，营养血流量减少26%，但腿部肌肉中蛋白质合成或分解率没有改变。股动脉完全阻断使下肢血流量减少42%，营养性血流量减少59%，使肌蛋白合成率和分解率分别从0.19 ± 0.05%/d和0.28 ± 0.07%/d降至0.14 ± 0.03%/d（P< 0.05）。无论是部分还是完全钳夹都没有降低（P= 0.27-0.39）细胞内苯丙氨酸浓度或腿部肌肉中的净蛋白平衡。我们得出结论，导致腿部肌肉蛋白质周转率下降的流量阈值是腿部流量减少30-40%。肌肉蛋白动力学对血流量减少的急性反应反映了维持肌肉稳态的代谢优先级。如果没有实验验证，这些发现不能外推到更慢性的疾病。
The present experiment was designed to measure the synthetic and breakdown rates of muscle protein in the hindlimb of rabbits with or without clamping the femoral artery.l-[ring-13C6]phenylalanine was infused as a tracer for measurement of muscle protein kinetics by means of an arteriovenous model, tracer incorporation, and tracee release methods. The ultrasonic flowmeter, dye dilution, and microsphere methods were used to determine the flow rates in the femoral artery, in the leg, and in muscle capillary, respectively. The femoral artery flow accounted for 65% of leg flow. A 50% reduction in the femoral artery flow reduced leg flow by 28% and nutritive flow by 26%, which did not change protein synthetic or breakdown rate in leg muscle. Full clamp of the femoral artery reduced leg flow by 42% and nutritive flow by 59%, which decreased (P< 0.05) both the fractional synthetic rate from 0.19 ± 0.05 to 0.14 ± 0.03%/day and fractional breakdown rate from 0.28 ± 0.07 to 0.23 ± 0.09%/day of muscle protein. Neither the partial nor full clamp reduced (P= 0.27–0.39) the intracellular phenylalanine concentration or net protein balance in leg muscle. We conclude that the flow threshold to cause a fall of protein turnover rate in leg muscle was a reduction of 30–40% of the leg flow. The acute responses of muscle protein kinetics to the reductions in blood flow reflected the metabolic priorities to maintain muscle homeostasis. These findings cannot be extrapolated to more chronic conditions without experimental validation.