Thompson G N, Pacy P J, Merritt H, Ford G C, Read M A, Cheng K N, Halliday D
Nutrition Research Group, Clinical Research Centre, Harrow, United Kingdom.
Am J Physiol. 1989 May;256(5 Pt 1):E631-9. doi: 10.1152/ajpendo.1989.256.5.E631.
Whole body protein turnover was measured in six normal adults using a model based on a primed constant infusion of [2H5]phenylalanine and, independently, by an established method of a primed constant infusion of [1-13C]leucine. Isotopic plateau in plasma was achieved within 2 h for [2H5]phenylalanine and, in four of the subjects who received a priming dose of [2H4]tyrosine, for [2H4]tyrosine. In all subjects whole body protein turnover measured with the phenylalanine model (mean protein synthesis, 2.65 +/- (SD) 0.16 g.kg-1.24 h-1; catabolism, 3.58 +/- 0.26 g.kg-1.24 h-1) was similar to that measured using the leucine model (synthesis, 3.09 +/- 0.27 g.kg-1.24 h-1; catabolism, 3.70 +/- 0.35 g.kg-1.24 h-1). Mean forearm fractional muscle protein synthesis calculated by the phenylalanine model was 0.06 +/- 0.03%/h, which compares closely with literature values derived by other methods. The phenylalanine model allows the rapid assessment of whole body and muscle protein turnover from plasma samples alone, obviating the need for measurement of expired air CO2 production or enrichment.
采用基于[2H5]苯丙氨酸单次快速静脉注射和持续静脉输注的模型，对6名正常成年人的全身蛋白质周转率进行了测量，并独立地采用既定的[1-13C]亮氨酸单次快速静脉注射和持续静脉输注方法进行测量。对于[2H5]苯丙氨酸，在2小时内血浆达到同位素平台期；对于接受[2H4]酪氨酸单次快速静脉注射剂量的4名受试者，[2H4]酪氨酸也在2小时内达到同位素平台期。在所有受试者中，用苯丙氨酸模型测得的全身蛋白质周转率（平均蛋白质合成，2.65±（标准差）0.16g·kg-1·24h-1；分解代谢，3.58±0.26g·kg-1·24h-1）与用亮氨酸模型测得的结果（合成，3.09±0.27g·kg-1·24h-1；分解代谢，3.70±0.35g·kg-1·24h-1）相似。用苯丙氨酸模型计算的平均前臂肌肉蛋白质合成率为0.06±0.03%/小时，这与其他方法得出的文献值相近。苯丙氨酸模型仅通过血浆样本就能快速评估全身和肌肉蛋白质周转率，无需测量呼出气体中的二氧化碳产生量或富集度。
