ADAPTATION OF RATS TO DIETS CONTAINING DIFFERENT LEVELS OF PROTEIN - EFFECTS OF FOOD-INTAKE, PLASMA AND BRAIN AMINO-ACID CONCENTRATIONS AND BRAIN NEUROTRANSMITTER METABOLISM
ADAPTATION OF RATS TO DIETS CONTAINING DIFFERENT LEVELS OF PROTEIN - EFFECTS OF FOOD-INTAKE, PLASMA AND BRAIN AMINO-ACID CONCENTRATIONS AND BRAIN NEUROTRANSMITTER METABOLISM
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DOI：
10.1093/jn/115.3.382
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发表时间：
1985-01-01
影响因子：
4.2
通讯作者：
HARPER, AE
中科院分区：
文献类型：
--
作者：
PETERS, JC;HARPER, AE
食物摄入量，血浆和大脑的氨基酸浓度，肝脏氨基酸分解代谢酶的活性，全脑神经递质和代谢物的浓度进行了测量，适应了11天的饮食含有5%至75%（增量为5%）酪蛋白的年轻大鼠。食物摄入量最初在大鼠饲料中含有5，10%或大于35%的酪蛋白被压抑。在实验期间，高蛋白饮食组的食物摄入量在连续几天得到改善;抑郁症的持续时间和严重程度与饮食中的蛋白质含量成正比。喂食低水平蛋白质的老鼠生长不良，它们的食物摄入量仍然很低。喂食含有超过35%酪蛋白的饲料的大鼠的生长和食物摄入的逐渐改善伴随着肝脏中丝氨酸-苏氨酸转氨酶（SDH，EC 4.2.1.16）和谷氨酸-丙酮酸转氨酶（GPT，EC 2.6.1.1）活性的急剧增加。氨基酸分解代谢活性的增加伴随着血浆和大脑中大多数氨基酸浓度的降低。然而，浓度的支链氨基酸，在血浆和大脑中，增加成正比的饮食喂养的蛋白质浓度。由于这些相互的反应，大脑中不可缺少的氨基酸（IAA）的总浓度保持在一个狭窄的范围内的值，尽管6倍范围的蛋白质摄入量。高香草酸和5-羟基吲哚乙酸的全脑浓度与蛋白质摄入量呈负相关，3，4-二羟基苯乙酸的全脑浓度与蛋白质摄入量呈负相关，3，4-二羟基苯乙酸的全脑浓度与食物摄入量呈正相关。蛋白质摄入量似乎与动物维持脑中总IAA含量在一定上限和下限之间的能力有关。结果表明，这是完成最初通过向下调整蛋白质摄入量，随后通过增加分解代谢能力的氨基酸。
Food intake, plasma and brain amino acid concentrations, liver amino acid catabolic enzyme activities, and whole-brain neurotransmitter and metabolite concentrations were measured in young rats adapted for 11 days to diets containing from 5 to 75% (in increments of 5%) casein. Food intake was depressed initially in rats fed diets containing 5, 10% or greater than 35% casein. For the duration of the experiment, food intakes of the groups fed the higher protein diets improved on succesive days; the length and severity of the depression were proportional to the protein content of the diet fed. Rats fed low levels of protein grew poorly, and their food intake remained depressed. The gradual improvement in growth and food intake of rats fed diets containing more than 35% casein was accompanied by dramatic increases in the activities of serine-threonine dehydratase (SDH, EC 4.2.1.16) and glutamate-pyruvate aminotransferase (GPT, EC 2.6.1.1) in liver. The increase in amino acid catabolic activity was accompanied by decreases in the concentrations of most amino acids in plasma and brain. However, concentrations of branched-chain amino acids, in both plasma and brain, increased in direct proportion to the protein concentration of the diet fed. As a result of these reciprocal responses, the total concentration of indispensable amino acids in brain (IAA) was maintained within a narrow range of values, despite a 6-fold range of protein intakes. Whole-brain concentrations of homovanillic cid and 5-hydroxyindoleacetic acid were correlated inversely with protein intake and that of 3,4-dihydroxyphenylacetic acid was correlated inversely with protein intake and that of 3,4-dihydroxyphenylacetic acid was correlated directly with food intake. Protein intake appeared to be related to the animal''s ability to maintain brain total IAA content between some upper and lower limits. Results indicate that this was accomplished initially through downward adjustment of protein intake and subsequently through an increase in catabolic capacity for the amino acids.