Munck L K, Grøndahl M L, Skadhauge E
Department of Medical Physiology, Panum Institute, University of Copenhagen, Denmark.
Biochim Biophys Acta. 1995 Aug 23;1238(1):49-56. doi: 10.1016/0005-2736(95)00107-e.
This study describes unidirectional influx of amino acids and D-glucose across the small intestinal brush-border membrane of fully weaned eight week old pigs. Influx is minimal in the duodenum and maximal in the distal and/or mid small intestine. Influx of beta-alanine, taurine and N-methyl-aminoisobutyric acid is chloride-dependent. The activation stoichiometry for taurine influx is 1.0 +/- 0.2 chloride/2.4 +/- 0.3 sodium/1 taurine. Influx of D-glucose, lysine, glycine and glutamate is chloride-independent. An ABC test demonstrates a common beta-amino acid carrier: (a) the apparent affinity constant K1/2Taurine is 44 +/- 13 microM (means +/- S.D.) and the inhibitory constant (KiTaurine) against beta-alanine influx is 41 +/- 5 microM (means +/- S.E.). (b) K1/2beta-alanine is 97 +/- 23 microM and Kibeta-alanine against taurine influx is 160 +/- 22 microM. (c) KiHypotaurine against taurine and beta-alanine influx is 43 +/- 4 (n = 7) and 22 +/- 5 microM (n = 7), respectively. In conclusion, a high affinity, low capacity, sodium- and chloride-dependent carrier of beta-amino acids is present in pig small intestine.
本研究描述了8周龄完全断奶仔猪小肠刷状缘膜上氨基酸和D-葡萄糖的单向流入情况。十二指肠中的流入量最小，而在小肠远端和/或中部最大。β-丙氨酸、牛磺酸和N-甲基氨基异丁酸的流入依赖于氯离子。牛磺酸流入的激活化学计量为1.0±0.2氯离子/2.4±0.3钠离子/1牛磺酸。D-葡萄糖、赖氨酸、甘氨酸和谷氨酸的流入不依赖于氯离子。ABC试验证明存在一种常见的β-氨基酸载体：(a)牛磺酸的表观亲和常数K1/2为44±13微摩尔（平均值±标准差），对β-丙氨酸流入的抑制常数（Ki牛磺酸）为41±5微摩尔（平均值±标准误）。(b)K1/2β-丙氨酸为97±23微摩尔，β-丙氨酸对牛磺酸流入的Kibeta-丙氨酸为160±22微摩尔。(c)次牛磺酸对牛磺酸和β-丙氨酸流入的Ki分别为43±4（n = 7）和22±5微摩尔（n = 7）。总之，猪小肠中存在一种高亲和力、低容量、依赖钠离子和氯离子的β-氨基酸载体。
