Miles J M, Nissen S L, Gerich J E, Haymond M W
Am J Physiol. 1984 Aug;247(2 Pt 1):E166-72. doi: 10.1152/ajpendo.1984.247.2.E166.
Infusion of epinephrine in humans increases glucose production and decreases plasma concentrations of some essential amino acids such as leucine, while not affecting the plasma concentration of the potential gluconeogenic amino acid alanine. To determine whether epinephrine alters alanine and leucine metabolism, rates of appearance (Ra) and disappearance (Rd) of glucose, alanine, and leucine were determined in postabsorptive volunteers using [3H]glucose, [2H3]alanine, [15N]leucine, and [2H3]leucine during a 180-min infusion of epinephrine (50 ng X kg-1 X min-1). Plasma glucose (90 +/- 1 to 142 +/- 5 mg/dl) and insulin (10 +/- 1 to 16 +/- 2 micrograms/ml) increased (P less than 0.05), whereas plasma alanine concentrations did not change and plasma leucine concentrations increased (127 +/- 5 to 72 +/- 3 microM). Glucose Ra increased transiently and returned to basal values by 120 min. In contrast, alanine Ra and Rd increased identically and progressively from 5.7 +/- 0.5 to 14.5 +/- 1.9 mumol X kg-1 X min-1 by 180 min. Although leucine nitrogen Ra increased transiently and returned to basal values, leucine carbon Ra and Rd decreased (P less than 0.05) during the infusion of epinephrine. The calculated rate and percent of leucine nitrogen going to alanine increased, whereas the percent of alanine nitrogen derived from leucine remained constant. The increase in alanine Ra was entirely attributable to increased de novo synthesis because proteolysis, as estimated by leucine carbon flux, decreased.
在人体中输注肾上腺素会增加葡萄糖生成，并降低某些必需氨基酸（如亮氨酸）的血浆浓度，而不影响潜在的糖异生氨基酸丙氨酸的血浆浓度。为了确定肾上腺素是否会改变丙氨酸和亮氨酸的代谢，在180分钟输注肾上腺素（50 ng·kg⁻¹·min⁻¹）期间，使用[³H]葡萄糖、[²H₃]丙氨酸、[¹⁵N]亮氨酸和[²H₃]亮氨酸，测定了吸收后志愿者体内葡萄糖、丙氨酸和亮氨酸的出现率（Ra）和消失率（Rd）。血浆葡萄糖（90±1至142±5 mg/dl）和胰岛素（10±1至16±2 μg/ml）升高（P<0.05），而血浆丙氨酸浓度未改变，血浆亮氨酸浓度升高（127±5至72±3 μM）。葡萄糖Ra短暂升高，到120分钟时恢复到基础值。相反，丙氨酸Ra和Rd在180分钟时从5.7±0.5 μmol·kg⁻¹·min⁻¹相同且逐渐增加至14.5±1.9 μmol·kg⁻¹·min⁻¹。尽管亮氨酸氮Ra短暂升高并恢复到基础值，但在输注肾上腺素期间，亮氨酸碳Ra和Rd降低（P<0.05）。计算得出的亮氨酸氮转化为丙氨酸的速率和百分比增加，而丙氨酸氮源自亮氨酸的百分比保持不变。丙氨酸Ra的增加完全归因于从头合成增加，因为根据亮氨酸碳通量估计的蛋白水解减少。
