REPLETION OF FOLATE-DEPLETED RATS WITH AN AMINO-ACID BASED DIET SUPPLEMENTED WITH FOLIC-ACID
REPLETION OF FOLATE-DEPLETED RATS WITH AN AMINO-ACID BASED DIET SUPPLEMENTED WITH FOLIC-ACID
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DOI：
10.1093/jn/119.12.1956
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发表时间：
1989-12-01
影响因子：
4.2
通讯作者：
BILLS, ND
中科院分区：
文献类型：
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作者：
CLIFFORD, AJ;WILSON, DS;BILLS, ND
叶酸消耗和补充方案尚未标准化。断奶大鼠在 28 d 内以基于 17% 氨基酸作为氮源的无叶酸纯化饮食中度消耗叶酸。然后用补充有125、250、500、1000或2000μg叶酸/kg的氨基酸饮食给它们补充叶酸23天。在 24 日龄（基线）、52 日龄（耗尽）和 75 日龄（补充）的大鼠亚组中测量了血液学、生长和组织叶酸水平。在相同时间内喂食 2 毫克叶酸/公斤氨基酸饮食的对照大鼠中进行了相同的测量。我们的研究结果表明，补充叶酸后，先前耗尽的大鼠的生长与叶酸补充水平成正比，最高可达 1000 μg/kg 饮食。补充充足的大鼠的血清叶酸水平也随补充量在500至2000μg/kg饮食之间成比例增加，并且肝脏叶酸水平在125至2000μg/kg饮食范围内随补充水平成比例增加。 2000μg/kg补充剂足以使肝脏叶酸水平恢复至与对照相同的水平，但在23天补充期内体重和血清叶酸水平未能赶上对照。血清和肝脏叶酸水平之间存在非线性关系：血清叶酸保持恒定在约6μg/l，而肝脏叶酸增加至约7μg/g，然后血清叶酸出现偏差，增加至120μg/l，而肝脏叶酸仅轻微增加。由于血清和肝脏叶酸水平之间的非线性关系以及测量组织叶酸的更大费用和复杂性，生长可能是最可靠也是最简单的测量标准。数据表明，使用无叶酸饮食（以 17% 氨基酸为氮源）的大鼠测定系统是评估食物叶酸相对生物利用度的可靠系统。在报告的标准化条件下，生长是测量叶酸消耗和补充的敏感、可靠和实用的反应指标。
Folate depletion and repletion protocols are not well standardized. Weanling rats were moderately depleted of folate in 28 d with a folate-free purified diet based on 17% amino acids as the nitrogen source. They were then folate repleted for 23 d with the amino acid diet supplemented with either 125, 250, 500, 1000 or 2000 .mu.g folic acid/kg. Hematology, growth and tissue folate levels were measured in subsets of the rats when they were 24 (baseline), 52 (depleted) and 75 d old (repleted.). The same measurements were made in control rats that had been fed 2 mg folic acid/kg of the amino acid diet for the same period of time. Our findings show that with repletion, growth of previously depleted rats is in direct proportion with the level of supplementation up to 1000 .mu.g folic acid/kg diet. Serum folate levels of repleted rats also increased in proportion to supplementation between 500 to 2000 .mu.g/kg diet, and liver folate levels inceased proportionally with the level of supplement within the range of 125 to 2000 .mu.g/kg diet. The 2000 .mu.g/kg supplement was sufficient to restore liver folate levels equivalent to that of controls, but body weight and serum folate levels failed to catch up with that of controls in the 23-d repletion period. There was a nonlinear relationship between serum and liver folate levels: serum folate remained constant at about 6 .mu.g/l as liver folate increased to about 7 .mu.g/g, then serum folate diverged by increasing to 120 .mu.g/l with only minor increases in liver folate. Because of the nonlinear relationship between serum and liver folate levels and the greater expense and complexity of measruing tissue folate, growth may be the most reliable as well as the simplest measurement criteria. Data suggest that a rat assay system using a folate-free diet, based on 17% amino acids as the nitrogen source, is a reliable system for assessing relative bioavailability of food folates. Under the standarized conditions reported, growth is a sensitive, reliable and practical response indicator for measuring depletion and repletion with folate.