Smith K, Reynolds N, Downie S, Patel A, Rennie M J
Department of Anatomy and Physiology, University of Dundee, Dundee DD1 4HN, Scotland, United Kingdom.
Am J Physiol. 1998 Jul;275(1):E73-8. doi: 10.1152/ajpendo.1998.275.1.E73.
We investigated the effects of the nature of the flooding amino acid on the rate of incorporation of tracer leucine into human skeletal muscle sampled by biopsy. Twenty-three healthy young men (24.5 +/- 5. 0 yr, 76.2 +/- 8.3 kg) were studied in groups of four or five. First, the effects of flooding with phenylalanine, threonine, or arginine (all at 0.05 g/kg body wt) on the incorporation of tracer [13C]leucine were studied. Then the effects of flooding with labeled [13C]glycine [0.1 g/kg body wt, 20 atoms percent excess (APE)] and [13C]serine (0.05 g/kg body wt, 15 APE) on the incorporation of simultaneously infused [13C]leucine were investigated. When a large dose of phenylalanine or threonine was administered, incorporation of the tracer leucine was significantly increased (from 0.036 to 0. 067 %/h and 0.037 to 0.070 %/h, respectively; each P < 0.01). However, when arginine, glycine, or serine was administered as a flooding dose, no stimulation of tracer leucine incorporation could be observed. These results, together with those previously obtained, suggest that large doses of individual essential, but not nonessential, amino acids are able to stimulate incorporation of constantly infused tracer amino acids into human muscle protein.
我们研究了冲击性氨基酸的性质对通过活检采集的人体骨骼肌中示踪亮氨酸掺入率的影响。23名健康年轻男性（年龄24.5±5.0岁，体重76.2±8.3千克）以4或5人为一组进行研究。首先，研究了用苯丙氨酸、苏氨酸或精氨酸（均为0.05克/千克体重）进行冲击对示踪[13C]亮氨酸掺入的影响。然后，研究了用标记的[13C]甘氨酸[0.1克/千克体重，20原子百分比过量（APE）]和[13C]丝氨酸（0.05克/千克体重，15 APE）进行冲击对同时输注的[13C]亮氨酸掺入的影响。当给予大剂量的苯丙氨酸或苏氨酸时，示踪亮氨酸的掺入显著增加（分别从0.036%/小时增加到0.067%/小时和从0.037%/小时增加到0.070%/小时；P均<0.01）。然而，当给予精氨酸、甘氨酸或丝氨酸作为冲击剂量时，未观察到对示踪亮氨酸掺入的刺激作用。这些结果与先前获得的结果一起表明，大剂量的单个必需氨基酸而非非必需氨基酸能够刺激持续输注的示踪氨基酸掺入人体肌肉蛋白质中。
