Gardner M L, Mitchell C J
Q J Exp Physiol. 1981 Jan;66(1):17-24. doi: 10.1113/expphysiol.1981.sp002525.
The peptide, N-benzoyl-L-tyrosyl-p-aminobenzoic acid, which is used in an oral test of pancreatic function, has been perfused through isolated rat small intestine in order to determine whether it can be absorbed across the intestine in intact form, and whether it is hydrolysed appreciably by intestinal enzymes. For comparison, transport of N-benzoyl-DL-tyrosine, L-tyrosine, L-tyrosyl-L-leucine and p-aminobenzoic acid has also been studied. Very small amounts of bound tyrosine (probably mainly intact peptide plus some benzoyl-tyrosine) and of free p-aminobenzoic acid crossed the intestine during perfusion with N-benzoyl-L-tyrosyl-p-aminobenzoic acid. Adsorbed pancreatic enzymes were possibly responsible for the very small amount of hydrolysis of the peptide. However, no detectable free tyrosine crossed the intestine during perfusion with N-benzoyl-L-tyrosyl-p-aminobenzoic acid or with N-benzoyl-DL-tyrosine. In contrast, substantial quantities of free tyrosine crossed the intestine during perfusion with L-tyrosine or with L-tyrosyl-L-leucine. Net transport of tyrosine from L-tyrosyl-L-leucine was less than that from equimolar free L-tyrosine; no detectable intact L-tyrosyl-L-leucine crossed the intestine. During perfusion with free p-aminobenzoic acid the concentration in the serosal secretion apparently exceeded that in the lumen by a factor of 1.7; this suggests active transport of p-aminobenzoic acid.
用于胰腺功能口服测试的肽N-苯甲酰基-L-酪氨酰-对氨基苯甲酸，已被灌注通过离体大鼠小肠，以确定它是否能以完整形式被肠道吸收，以及它是否会被肠道酶显著水解。为作比较，还研究了N-苯甲酰基-DL-酪氨酸、L-酪氨酸、L-酪氨酰-L-亮氨酸和对氨基苯甲酸的转运情况。在用N-苯甲酰基-L-酪氨酰-对氨基苯甲酸灌注期间，极少量结合型酪氨酸（可能主要是完整肽加上一些苯甲酰基酪氨酸）和游离对氨基苯甲酸穿过了肠道。吸附的胰腺酶可能是导致该肽极少量水解的原因。然而，在用N-苯甲酰基-L-酪氨酰-对氨基苯甲酸或N-苯甲酰基-DL-酪氨酸灌注期间，没有可检测到的游离酪氨酸穿过肠道。相比之下，在用L-酪氨酸或L-酪氨酰-L-亮氨酸灌注期间，大量游离酪氨酸穿过了肠道。L-酪氨酰-L-亮氨酸中酪氨酸的净转运量少于等摩尔游离L-酪氨酸中的转运量；没有可检测到的完整L-酪氨酰-L-亮氨酸穿过肠道。在用游离对氨基苯甲酸灌注期间，浆膜分泌液中的浓度明显比肠腔内的浓度高出1.7倍；这表明对氨基苯甲酸存在主动转运。
