Munck L K, Munck B G
Department of Medical Physiology, Panum Institute, University of Copenhagen, Denmark.
Am J Physiol. 1994 Mar;266(3 Pt 2):R997-1007. doi: 10.1152/ajpregu.1994.266.3.R997.
The present study extends the observations of chloride-dependent intestinal amino acid carriers to the guinea pig and the rat using the technique of in vitro influx across the brush-border membrane of intact epithelium. Transport rates of D-glucose and L-amino acids are lowest in guinea pig proximal small intestine and are constant from midjejunum through distal ileum, except for leucine. The guinea pig possesses a sodium- and chloride-dependent, high-affinity, very low-capacity carrier of beta-amino acids for which taurine and beta-alanine compete and for which the Na(+)-taurine activation stoichiometry is 2.1 +/- 0.3:1. The imino acid carrier of the guinea pig is also chloride dependent with a Na(+)-Cl(-)-2-methylamino-isobutyric acid activation stoichiometry of 1.8 +/- 0.1:0.7 +/- 0.3:1. In contrast, the rat imino acid carrier is chloride independent and transport rates vary insignificantly along the small intestine. The rat taurine carrier has its maximal transport rate in midjejunum. It is chloride dependent but does not transport beta-alanine.
本研究采用完整上皮刷状缘膜体外流入技术，将对氯离子依赖性肠氨基酸载体的观察扩展到豚鼠和大鼠。豚鼠近端小肠中D - 葡萄糖和L - 氨基酸的转运速率最低，从空肠中部到回肠末端保持恒定，但亮氨酸除外。豚鼠拥有一种钠和氯离子依赖性、高亲和力、极低容量的β - 氨基酸载体，牛磺酸和β - 丙氨酸可与之竞争，且Na(+) - 牛磺酸激活化学计量比为2.1±0.3:1。豚鼠的亚氨基酸载体也依赖氯离子，Na(+) - Cl(-) - 2 - 甲基氨基异丁酸激活化学计量比为1.8±0.1:0.7±0.3:1。相比之下，大鼠的亚氨基酸载体不依赖氯离子，且沿小肠的转运速率变化不显著。大鼠的牛磺酸载体在空肠中部具有最大转运速率。它依赖氯离子，但不转运β - 丙氨酸。
