Anthony L E, Edozien J C
J Nutr. 1975 Jun;105(6):631-48. doi: 10.1093/jn/105.6.631.
Young male rats (100-130 g) were fed diets of equal energy content containing o.5, 1,2,3,5, and 18% lactalbumin consumed either freely or in restricted amounts. The rats receiving low protein diets failed to grow and mature. Those consuming the 0.5 and1% protein diets given freely developed the characteristic features of kwashiorkor including edema, while those receiving the diets in restricted amounts developed the characteristic features of marasmus. The rats fed low protein diets had low plasma levels of essential amino acids; however, the lysine level was well maintained. The plasma levels of nonessential amino acids, especially glycine, alanine, and aspartic and glutamic acids were raised in marasmic rats but were reduced in rats fed low protein diets ad libitum. Young and severly malnourished rats appeared to have limited ability to synthesize urea. Therefore, they excreted more ammonia and other nitrogenous substances such as ethanolamine, and when given an amino acid load, intermediary metabolites of the ingested amino acids. Rats fed low protein diets showed diminution of total liver DNA, RNA, and protein. In addition to the reduction of protein synthesis resulting from decreased cellular RNA, ribosomes from the livers of protein-deficient rats had reduced ability to synthesize proteins. This defect was associated with the detatchment of the ribosomes from endoplasmic reticulum membrane and the elevation of the proportion of monosomes to polyribosomes. Malnutrition did not produce any change in the turnover rate of liver RNA. Protein deficiency caused significant depression of serum insulin, thyroxine, and corticosterone levels. Theoverall conclusion is that mammalian metabolism is well adapted to dietary intake and that this adaptation is achieved through dietary control of synthesis and release of key metabolic hormones.
将100 - 130克的幼年雄性大鼠喂养含0.5%、1%、2%、3%、5%和18%乳白蛋白且能量含量相等的日粮，大鼠可自由进食或限量进食。摄入低蛋白日粮的大鼠无法生长和成熟。自由进食0.5%和1%蛋白日粮的大鼠出现了夸希奥科病的特征，包括水肿，而限量进食这些日粮的大鼠出现了消瘦的特征。喂食低蛋白日粮的大鼠血浆中必需氨基酸水平较低；然而，赖氨酸水平维持良好。消瘦大鼠血浆中非必需氨基酸水平，尤其是甘氨酸、丙氨酸、天冬氨酸和谷氨酸水平升高，但自由采食低蛋白日粮的大鼠这些氨基酸水平降低。年幼且严重营养不良的大鼠似乎合成尿素的能力有限。因此，它们排泄更多的氨和其他含氮物质，如乙醇胺，并且在给予氨基酸负荷时，排泄摄入氨基酸的中间代谢产物。喂食低蛋白日粮的大鼠肝脏中总DNA、RNA和蛋白质含量减少。除了由于细胞RNA减少导致蛋白质合成减少外，蛋白质缺乏大鼠肝脏中的核糖体合成蛋白质的能力也降低。这种缺陷与核糖体从内质网膜上脱离以及单体与多聚核糖体比例升高有关。营养不良并未使肝脏RNA的周转率发生任何变化。蛋白质缺乏导致血清胰岛素、甲状腺素和皮质酮水平显著降低。总体结论是，哺乳动物的新陈代谢能很好地适应饮食摄入，并且这种适应是通过饮食控制关键代谢激素的合成和释放来实现的。
