Gahl M J, Finke M D, Crenshaw T D, Benevenga N J
Department of Animal Sciences, University of Wisconsin, Madison 53706, USA.
J Nutr. 1996 Dec;126(12):3090-9. doi: 10.1093/jn/126.12.3090.
Over a 21-d experiment, the efficiency of lysine and threonine retention was determined in 80 male Sprague-Dawley rats (65.9 +/- 0.3 g, means +/- SE) fed purified diets containing an amino acid mix limiting in either lysine or threonine. With additional increments of the first limiting amino acid, lysine concentration in total body protein (g/16 g N) increased (P < 0.01) in rats fed lysine-limiting diets but, when fed threonine-limiting diets, lysine concentration in body protein first increased and then decreased (P < 0.01). As increments of the first limiting amino acid were added, the threonine concentration in total body protein increased then decreased when both lysine- (P < 0.01) and threonine- (P < 0.06) limiting diets were fed. Lysine and threonine retention were calculated based on comparative slaughter. Sixteen rats were killed on d 0 to estimate the grams of amino acid in the body. Retention responses were analyzed using a logistic equation in which lysine or threonine intake was used to predict retention. The maximum marginal efficiency (dr/dI, retention/intake) was observed at <40% of maximum retention. For lysine retention, it was 81% when lysine was limiting and 70% when threonine was limiting. For threonine retention, it was 58% when threonine was limiting and 49% when lysine was limiting. The maximum cumulative efficiency (retention adjusted for maintenance relative to cumulative intake) for lysine retention was 62% when lysine was limiting or 58% when threonine was limiting. For threonine retention, it was 51% when threonine was limiting and 35% when lysine was limiting. Thus, amino acid concentration in body protein is not constant, and amino acids are used with higher efficiency when first limiting.
在一项为期21天的实验中，对80只雄性斯普拉格-道利大鼠（体重65.9±0.3克，均值±标准误）进行了赖氨酸和苏氨酸保留效率的测定，这些大鼠被喂食含有赖氨酸或苏氨酸受限的氨基酸混合物的纯化日粮。随着第一限制性氨基酸的额外增加，在喂食赖氨酸受限日粮的大鼠中，全身蛋白质中的赖氨酸浓度（克/16克氮）增加（P<0.01），但在喂食苏氨酸受限日粮时，身体蛋白质中的赖氨酸浓度先增加后降低（P<0.01）。当添加第一限制性氨基酸时，在喂食赖氨酸受限（P<0.01）和苏氨酸受限（P<0.06）日粮时，全身蛋白质中的苏氨酸浓度均先增加后降低。基于比较屠宰法计算赖氨酸和苏氨酸的保留量。在第0天处死16只大鼠以估计体内氨基酸的克数。使用逻辑方程分析保留反应，其中赖氨酸或苏氨酸摄入量用于预测保留量。在最大保留量的<40%时观察到最大边际效率（dr/dI，保留量/摄入量）。对于赖氨酸保留，当赖氨酸受限时为81%，当苏氨酸受限时为70%。对于苏氨酸保留，当苏氨酸受限时为58%，当赖氨酸受限时为49%。赖氨酸保留的最大累积效率（相对于累积摄入量调整维持量后的保留量），当赖氨酸受限时为62%，当苏氨酸受限时为58%。对于苏氨酸保留，当苏氨酸受限时为51%，当赖氨酸受限时为35%。因此，身体蛋白质中的氨基酸浓度并非恒定不变，且第一限制性氨基酸的利用效率更高。
