ラットのトレオニン分解酵素活性とトレオニン関連の遊離アミノ酸濃度に対する飼料中のトレオニン含量の影響 Effects of Dietary Threonine Levels on the Threonine-degrading Enzyme Activities and Tissue Threonine Related Amino Acid Concentration in Rats

この論文にアクセスする

この論文をさがす

著者

抄録

トレオニン(Thr)を過剰に添加した飼料を給与したときに,ラットの血漿中の遊離グリシン(Gly),セリン(Ser)濃度の応答を鶏の場合と比較するため,雄のWistar/STラット(304.5±5.2g)に飼料中Thr濃度が0.32~0.67%までの5種類の試験飼料を給与した.試験飼料の組成は産卵鶏の場合の基礎飼料の組成と同一とした.肝臓,腎臓および十二指腸の各組織中のThr, GlyおよびSer濃度はμmol/g,また,ThrからGlyへの転換,およびGlyとSerの相互転換に関係する酵素活性は,各組織1g当たり30分間の反応で生成される各アミノ酸のμmol/gとして測定した.肝臓のThr濃度は,飼料中Thrが0.32~0.42%までは徐々に増加し,その後飼料中Thr濃度が高くなるに従って直線的に増加した.腎臓と十二指腸のThr濃度もまた飼料中Thr濃度が0.67%のとき,0.42%以下のときに比較し各々45,75%増加した.3組織中Gly濃度は,飼料中Thr濃度に関わらず一定であったが,腎臓中Gly濃度は他の2組織のGly濃度に比べ2倍以上高かった.肝臓中Ser濃度は,飼料中Thr濃度の増加に対応してわずかに増加する傾向がみられたが,腎臓や十二指腸のSer濃度は飼料中Thr濃度に影響されなかった.Thr分解酵素活性は,飼料中Thr濃度が0.32~0.42%のとき,肝臓のThr-aldolase活性がわずかに減少し,その後,飼料中Thr濃度が高くなるに従って増加した.肝臓のSerhydroxymethyltransferase以外の他の酵素活性は飼料中Thr濃度に影響されなかった.肝臓のSerをGlyに転換するSer-hydroxymethyltransferaseだけが,産卵鶏の場合とは逆に飼料中のThr濃度が高くなるに従って減少した.ラットの肝臓におけるこのような代謝調節は,Thr過剰飼料に対するラットとニワトリとの組織,および血漿中Ser濃度の応答の差の理由の一因であることが示唆された.

In order to compare the responses of plasma amino acid (AA) concentrations of glycine (Gly) and serine (Ser) to the dietary excess threonine (Thr) in rats and chickens, adult male Wistar/ST rats weighing 304.5±5.2g were fed diets with five graded levels of Thr from 0.32 to 0.67%. The composition of experimental diets was similar to that of the basal diet used for laying hens. Tissue concentrations (TC) of three AA, Thr, Gly and Ser, expressed as μmol/g tissue and the enzyme activities expressed as μmol/g tissue/30min relating to conversion of Thr to Gly and interconversion of Gly and Ser in homogenates of liver, kidney and duodenum were determined. In the liver, when dietary Thr increased from 0.32 to 0.42%, TC of Thr increased from 0.50 to 0.73 μmol/g, and then increased linearly with increasing dietary Thr levels. When dietary Thr levels were higher than 0.42%, TC of Thr in the kidney and duodenum were higher 45 and 75% at 0.67% dietary Thr level compared to those at less than 0.42% dietary Thr level, respectively. TC of Gly in the three tissues remained constant regardless of dietary Thr levels, but those in the kidney were two times higher than those in other two tissues. TC of Ser in the liver tended to increase, however, those in the kidney and duodenum were not affected by dietary Thr levels. In the liver, Thr aldolase activity decreased slightly, and then increased at dietary Thr levels exceeded 0.42%. However, all enzyme activities except Ser-hydroxymethyltransferase in the liver were not affected by dietary Thr levels. In contrast to the data of laying hens reported previously, the activity of liver Ser-hydroxymethyltransferase converting Ser to Gly decreased with increasing dietary Thr levels. These responses of enzyme activities in the rat liver might be one of the reasons for the difference in the responses of TC and plasma concentrations of Gly and Ser to the dietary excess Thr in rats and chickens.

収録刊行物

  • 日本畜産學會報 = The Japanese journal of zootechnical science  

    日本畜産學會報 = The Japanese journal of zootechnical science 69(2), 108-116, 1998-02-25 

    Japanese Society of Animal Science

参考文献:  21件

参考文献を見るにはログインが必要です。ユーザIDをお持ちでない方は新規登録してください。

各種コード

  • NII論文ID(NAID)
    10021726789
  • NII書誌ID(NCID)
    AN00195188
  • 本文言語コード
    ENG
  • 資料種別
    ART
  • ISSN
    1346907X
  • データ提供元
    CJP書誌  J-STAGE 
ページトップへ