Krawielitzki K, Schadereit R, Wünsche J, Völker T, Bock H D
Arch Tierernahr. 1983 Oct-Nov;33(10-11):731-42. doi: 10.1080/17450398309425157.
In 3 experiments growing female pigs, (live weight 35-56 kg) received continuous infusions of 15N-labelled or 15N- and 14C-doubly labelled isoleucine by means of caecal cannulae. The whereabouts of the infused isoleucine were investigated. Between 8.9 and 12.3% of the infused 15N-excess (15N') was excreted in faeces mainly in the forms of bacteria protein, between 0.7 and 0.9% only of the infused amount unchanged as 15N-isoleucine. The highest quota is microbially decomposed in the colon and absorbed in the form of NH3 or amines. Between 45 and 70% of the infused 15N are excreted in urine, mainly as urea (85-95% of the 15N-amount in urine). Virtually no 15N from the infused isoleucine is incorporated in the organ and tissue proteins (exception: colon wall). These findings are corroborated by the 14C-activity measuring as no intact 14C labelled isoleucine could be detected in the tissue protein. These results show that intact isoleucine is not absorbed in the colon. The nitrogen originating from the absorbed NH3 is nearly completely excreted in urine and thus not available to the biosynthesis of body protein.
在3项针对生长中的雌性猪（体重35 - 56千克）的实验中，通过盲肠插管持续输注15N标记或15N和14C双标记的异亮氨酸。对输注的异亮氨酸去向进行了研究。输注的15N过量部分（15N'）中，有8.9%至12.3%以细菌蛋白等形式随粪便排出，只有0.7%至0.9%的输注量以15N - 异亮氨酸形式未发生变化。最高比例在结肠中被微生物分解，并以NH3或胺的形式被吸收。输注的15N中有45%至70%随尿液排出，主要以尿素形式（占尿液中15N量的85%至95%）。输注的异亮氨酸中的15N实际上没有掺入器官和组织蛋白中（结肠壁除外）。通过14C活性测量证实了这些发现，因为在组织蛋白中未检测到完整的14C标记异亮氨酸。这些结果表明，完整的异亮氨酸在结肠中不被吸收。源自吸收的NH3的氮几乎完全随尿液排出，因此无法用于机体蛋白质的生物合成。
