Zhang Xiao-Jun, Chinkes David L, Herndon David N, Wolfe Robert R
Shriners Hospital for Children and Department of Surgery, University of Texas Medical Branch, Galveston, TX 77550, USA.
Metabolism. 2009 Sep;58(9):1239-47. doi: 10.1016/j.metabol.2009.03.022. Epub 2009 Jun 18.
The flooding dose method continues to be useful in measuring protein fractional synthetic rate (FSR) in a tissue. However, flooding of free amino acid pools eliminates enrichment difference between plasma and tissue free amino acid pools, which makes it impossible to concomitantly measure protein fractional breakdown rate (FBR). We hypothesized that a subflooding dose of an amino acid reduces the enrichment difference between plasma and tissue free amino acid pool to a minimal measurable level, thus allowing concomitant measurement of protein FSR and FBR. Phenylalanine (40% enriched) at 50 mg/kg was intravenously injected as a bolus in 6 anesthetized rabbits. Arterial blood and chest skin samples were taken before the injection and for 120 minutes after the injection. Fractional breakdown rate of skin protein calculated from 15-60-120-minute sampling times was 11.3%/d +/- 2.0%/d, which was close (P = .66) to the corresponding FSR of 10.0%/d +/- 2.3%/d. The subflooding dose injection did not disturb the FBR approach because modifications on the FBR equation to account for the changes of plasma phenylalanine concentration resulted in the same value (11.5%/d +/- 1.4%/d). The FBR was positively correlated with the FSR (r = 0.80, P < .05). These findings indicate maintenance of protein mass in the skin, which is a metabolic characteristic of the skin. This subflooding dose method provides a methodological choice to concomitantly measure both FSR and FBR in a tissue.
灌流剂量法在测量组织中蛋白质的合成率(FSR)方面仍然很有用。然而,游离氨基酸池的灌流消除了血浆和组织游离氨基酸池之间的富集差异,这使得无法同时测量蛋白质的分解率(FBR)。我们假设,氨基酸的亚灌流剂量可将血浆和组织游离氨基酸池之间的富集差异降低到最小可测量水平,从而允许同时测量蛋白质的FSR和FBR。以50mg/kg的剂量静脉推注40%富集的苯丙氨酸,用于6只麻醉兔。在注射前及注射后120分钟采集动脉血和胸部皮肤样本。根据15 - 60 - 120分钟采样时间计算的皮肤蛋白质分解率为11.3%/天±2.0%/天,与相应的FSR(10.0%/天±2.3%/天)接近(P = 0.66)。亚灌流剂量注射并未干扰FBR方法,因为对FBR方程进行修正以考虑血浆苯丙氨酸浓度的变化后得到了相同的值(11.5%/天±1.4%/天)。FBR与FSR呈正相关(r = 0.80,P < 0.05)。这些发现表明皮肤中蛋白质质量的维持,这是皮肤的一种代谢特征。这种亚灌流剂量法为同时测量组织中的FSR和FBR提供了一种方法选择。