Khan M A, Bender A E
Nutr Metab. 1979;23(6):449-57. doi: 10.1159/000176291.
Adult rats that maintained nitrogen balance on a diet containing 5% casein fed ad libitum were restricted to 70% of their normal food intake for 31 days. This resulted in a negative N balance, loss of body weight and increased activities of hepatic glutamic pyruvic transaminase and arginase--all of which persisted for 10 days. After this time there was no further weight loss, the negative N balance returned to equilibrium and the activities of the two enzymes returned to normal indicating adaptation to the dietary restriction. Radio-isotope studies with labelled methionine showed that dietary restriction led to an increase in the radioactivity of the liver and a decrease of that of the muscles indicating maintenance of liver protein at the expense of muscle protein. Resting oxygen consumption decreased by 34% after 20 days of dietary restriction and this would account for the adaptation observed.
随意进食含5%酪蛋白饮食时能维持氮平衡的成年大鼠，被限制摄入正常食物量的70%，持续31天。这导致了负氮平衡、体重减轻以及肝脏谷丙转氨酶和精氨酸酶活性增加——所有这些情况持续了10天。在此之后，体重不再进一步减轻，负氮平衡恢复到平衡状态，两种酶的活性也恢复正常，表明对饮食限制产生了适应性。用标记蛋氨酸进行的放射性同位素研究表明，饮食限制导致肝脏放射性增加而肌肉放射性降低，这表明以肌肉蛋白为代价维持肝脏蛋白。饮食限制20天后，静息耗氧量下降了34%，这可以解释所观察到的适应性变化。
