Dawson J M, Greathead H M, Craigon J, Hachey D L, Reeds P J, Pell J M, Buttery P J
School of Biology, University of Nottingham, Loughborough, UK.
Br J Nutr. 1998 Mar;79(3):275-86. doi: 10.1079/bjn19980045.
The effect of dietary intake level on in vivo plasma leucine and plasma palmitate flux rates and on the response to a bolus injection of bovine growth hormone (GH) was investigated in six young steers. Animals were fed on a pelleted diet of dried grass-barley (0.7:0.3, w/w) in quantities sufficient to supply 0.8, 1.2, 1.6, 2.0, 2.4 or 2.65 x maintenance energy requirement, offered in hourly portions. Continuous intravenous infusions of [1-13C]leucine or [1-13C]palmitate were used to determine the flux of amino acid and fatty acid through the plasma pool before, immediately (1-3 h) after and 22-24 h after a subcutaneous injection of bovine GH (0.55 mg/kg body weight). Hourly blood samples were taken for 27 h to monitor the temporal responses of circulating hormones and metabolites following GH administration. The animal on the lowest plane of nutrition had elevated plasma GH and reduced insulin-like growth factor-1 concentrations compared with those fed on higher intake levels. Plasma leucine flux and leucine concentration increased with intake while palmitate flux and plasma non-esterified fatty acid (NEFA) concentrations were inversely related to intake. Leucine flux rate decreased in the animals fed on the two highest intake levels in response to GH 22-24 h after administration, but plasma leucine concentrations were reduced in all animals at this time. Only the animal fed on the lowest intake level showed an immediate response to GH (within 3 h of administration) with increased palmitate flux and plasma NEFA concentrations but a lipolytic response was apparent in other animals 22-24 h post-administration although the magnitude of the response was markedly reduced at high intakes. We conclude that lipid and protein metabolism are differentially responsive to GH and nutritional status.
研究了日粮摄入量水平对6头年轻阉牛体内血浆亮氨酸和血浆棕榈酸通量率以及对一次大剂量注射牛生长激素（GH）反应的影响。给动物饲喂干草-大麦颗粒饲料（0.7:0.3，w/w），饲喂量足以提供0.8、1.2、1.6、2.0、2.4或2.65倍维持能量需求，按小时分次投喂。在皮下注射牛GH（0.55mg/kg体重）之前、注射后立即（1 - 3小时）以及注射后22 - 24小时，通过持续静脉输注[1-¹³C]亮氨酸或[1-¹³C]棕榈酸来测定氨基酸和脂肪酸通过血浆池的通量。在27小时内每小时采集血样，以监测GH给药后循环激素和代谢物的时间反应。与摄入较高水平饲料的动物相比，处于最低营养水平的动物血浆GH升高，胰岛素样生长因子-1浓度降低。血浆亮氨酸通量和亮氨酸浓度随摄入量增加而升高，而棕榈酸通量和血浆非酯化脂肪酸（NEFA）浓度与摄入量呈负相关。在给药后22 - 24小时，摄入最高的两个水平的动物中，亮氨酸通量率因GH作用而降低，但此时所有动物的血浆亮氨酸浓度均降低。只有摄入最低水平饲料的动物对GH有立即反应（给药后3小时内），棕榈酸通量和血浆NEFA浓度增加，但在给药后22 - 24小时，其他动物也出现了脂解反应，尽管在高摄入量时反应幅度明显降低。我们得出结论，脂质和蛋白质代谢对GH和营养状况的反应存在差异。
