Davis A T, Austic R E
J Nutr. 1982 Nov;112(11):2177-86. doi: 10.1093/jn/112.11.2177.
Experiments were conducted to determine the metabolic fate of threonine in chicks fed threonine-imbalanced diets. Threonine imbalance was produced by the addition of 3% serine to a threonine-limited diet, and prevented by the addition of 0.2% threonine to the diet. Serine decreased plasma and liver free threonine concentrations, and increased hepatic threonine dehydrogenase and threonine aldolase activities. All changes, including reduced food intake, appeared to occur within 1 day of feeding the imbalanced diet. Despite the decrease in free threonine concentrations and the increase in threonine aldolase and threonine dehydrogenase activities, net threonine catabolism was not markedly increased. This was evidenced by similar amounts of 14CO2 exhaled by chicks fed control and imbalanced diets containing L-[U-14C] threonine, and by similar growth of chicks that were forced-fed both diets to maintain equivalent food intake. It is possible that increases in threonine catabolism contribute to depressions of plasma and tissue threonine concentrations. However, the growth depression caused by serine-induced threonine imbalance is due to depressed food intake.
进行了实验以确定饲喂苏氨酸不平衡日粮的雏鸡体内苏氨酸的代谢去向。通过在苏氨酸限制日粮中添加3%丝氨酸来造成苏氨酸不平衡，并通过在日粮中添加0.2%苏氨酸来预防。丝氨酸降低了血浆和肝脏中游离苏氨酸的浓度，并提高了肝脏中苏氨酸脱氢酶和苏氨酸醛缩酶的活性。所有变化，包括采食量减少，似乎都在饲喂不平衡日粮的1天内发生。尽管游离苏氨酸浓度降低，苏氨酸醛缩酶和苏氨酸脱氢酶活性增加，但苏氨酸的净分解代谢并未显著增加。这一点通过饲喂含有L-[U-14C]苏氨酸的对照日粮和不平衡日粮的雏鸡呼出的14CO2量相似，以及通过强制饲喂两种日粮以维持等量采食量的雏鸡生长相似得到证明。苏氨酸分解代谢的增加可能导致血浆和组织中苏氨酸浓度降低。然而，丝氨酸诱导的苏氨酸不平衡所导致的生长抑制是由于采食量降低。
