Davis A J, Austic R E
Department of Animal Science, Cornell University, Ithaca, NY 14853.
J Nutr. 1994 Sep;124(9):1667-77. doi: 10.1093/jn/124.9.1667.
Experiments were conducted on chicks and rats to determine whether hepatic threonine dehydrogenase activity is modified by the consumption of a threonine-imbalanced diet and to determine the tissue distribution of this enzyme. Threonine imbalances were created by supplementing basal diets with branched-chain amino acids (6 g/100 g diet for chicks) or a mixture of indispensable amino acid (5.6 g/100 g diet for chicks and 5.4 g/100 g diet for rats). Chicks fed threonine-imbalanced diets consistently had twice the hepatic threonine dehydrogenase activity of those fed the basal diet when measured in one experiment at 24 h and in two experiments at 216 h (P < 0.05). Rats received the experimental diets for 12 or 24 h in one experiment and for 12, 24, 72 or 168 h in another experiment. In the first experiment, rats fed the threonine-imbalanced diet had significantly greater hepatic threonine dehydrogenase activity (P < 0.05) at 12 h but not at 24 h. In the other rat experiment, threonine dehydrogenase activity in the rats fed the threonine-imbalanced diet was significantly greater than in controls at 72 h, but tended to be lower at 168 h, which coincided with the adaptation of the rats to the imbalanced diet. Threonine dehydrogenase activity was widespread in tissues of both species. The results indicate that alterations in hepatic threonine dehydrogenase activity occur in chicks and rats subjected to threonine imbalance.
在雏鸡和大鼠身上进行了实验，以确定食用苏氨酸不平衡饮食是否会改变肝脏苏氨酸脱氢酶的活性，并确定该酶的组织分布。通过在基础日粮中添加支链氨基酸（雏鸡为6克/100克日粮）或必需氨基酸混合物（雏鸡为5.6克/100克日粮，大鼠为5.4克/100克日粮）来造成苏氨酸不平衡。在一项实验中于24小时测定以及在两项实验中于216小时测定时，喂食苏氨酸不平衡日粮的雏鸡肝脏苏氨酸脱氢酶活性始终是喂食基础日粮雏鸡的两倍（P<0.05）。在一项实验中，大鼠接受实验日粮12或24小时，在另一项实验中接受12、24、72或168小时。在第一项实验中，喂食苏氨酸不平衡日粮的大鼠在12小时时肝脏苏氨酸脱氢酶活性显著更高（P<0.05），但在24小时时并非如此。在另一项大鼠实验中，喂食苏氨酸不平衡日粮的大鼠在72小时时苏氨酸脱氢酶活性显著高于对照组，但在168小时时趋于更低，这与大鼠对不平衡日粮的适应情况相符。苏氨酸脱氢酶活性在这两个物种的组织中广泛存在。结果表明，处于苏氨酸不平衡状态的雏鸡和大鼠肝脏中的苏氨酸脱氢酶活性会发生改变。
