Zebrowska T, Simon O, Münchmeyer R, Bergner H
Arch Tierernahr. 1976 Feb;26(2):69-82. doi: 10.1080/17450397609423240.
A trial was performed with 2 fistula pigs (each with 2 fistulas, one located about 30 cm below the pyloric orifice and the other at the end of the small intestine). Animal A received a casein diet containing 14% crude protein for a period of 2 weeks before the tracer amino acid was administered. Animal B received the same diet for a period of 10 days and was then fed a diet (at the same protein level) containing gluten as sole protein source. The two tracer amino acids, 14C-U-L-leucine and 3H-4,5-(N)-L-lysine, were injected intravenously. The passage rates for dry matter, organic matter and N measured at the beginning of the small intestine were higher than the rate of intake. The rate of passage of amino acids was also found to be increased relative to the rate of intake. In general, this increase involved the non-essential amino acids to a much larger extent. A considerable proportion of the amino acids passing into the large intestine is not excreted with the faeces but is probably converted in catabolic processes. It is for this reason that any values for the efficiency of amino acid absorption calculated on the basis of data on the faecal excretion of amino acids will not provide conclusive evidence for the availability of dietary amino acids in processes of the intermediate metabolism. The rate of secretion of 3H and 14C radioactivity into the digesta of the small intestine was found to increase rapidly within 1-2 hrs after administration of the tracer amino acids. The 14C radioactivity detected was found to be almost exclusively derived from 14C leucine while only about 60% of the 3H activity found in the digesta of fistula I were shown to be bound to lysine. Labelled lysine and leucine (of endogenic origin) are absorbed into the small intestine at a slower rate (i.e. endogenic proteins are less efficiently digested) than the non-radioactive amino acids (of exogenic origin) so that a process of concentration of endogenic amino acids is observed towards the end of the small intestine.
对2头瘘管猪进行了试验（每头猪有2个瘘管，一个位于幽门孔下方约30厘米处，另一个位于小肠末端）。在给予示踪氨基酸之前，动物A接受含14%粗蛋白的酪蛋白日粮2周。动物B接受相同日粮10天，然后饲喂以面筋为唯一蛋白质来源的日粮（蛋白质水平相同）。静脉注射两种示踪氨基酸，即14C-U-L-亮氨酸和3H-4,5-(N)-L-赖氨酸。在小肠起始部位测得的干物质、有机物和氮的通过率高于摄入量。还发现氨基酸的通过率相对于摄入量有所增加。一般来说，这种增加在很大程度上涉及非必需氨基酸。进入大肠的氨基酸有相当一部分不是随粪便排出，而是可能在分解代谢过程中被转化。因此，根据氨基酸粪便排泄数据计算的氨基酸吸收效率的任何值，都不能为中间代谢过程中日粮氨基酸的可利用性提供确凿证据。发现给予示踪氨基酸后1-2小时内，3H和14C放射性向小肠消化物中的分泌率迅速增加。检测到的14C放射性几乎完全来自14C亮氨酸，而在瘘管I消化物中发现的3H活性只有约60%与赖氨酸结合。标记的赖氨酸和亮氨酸（内源性来源）比非放射性氨基酸（外源性来源）吸收进入小肠的速度慢（即内源性蛋白质消化效率较低），因此在小肠末端观察到内源性氨基酸的浓缩过程。
