甘氨酸与钠在海洋虾类缘沟对虾中肠上皮黏膜边界的协同转运。

Co-transport of glycine and sodium across the mucosal border of the midgut epithelium in the marine shrimp, Penaeus marginatus.

Ahearn G A

J Physiol. 1976 Jul;258(3):499-520. doi: 10.1113/jphysiol.1976.sp011433.

Abstract

Influxes of glycine and Na across the mucosal border of the epithelial cells lining the midgut lumen of a marine shrimp have been examined. 2. Both mucosal JG and JNa displayed Michaelis-Menten kinetics and the influx of each solute was markedly dependent upon the presence of the other solute in the bathing solution. A portion of JG occurred in the absence of Na, but JNa appeared to be completely dependent upon glycine. 3. Glycine influx Kt and Jmax were dependent upon [Na] while Na influx Kt and Jmax depended upon [glycine]. 4. K acted as a competitive inhibitor of Na binding to the co-transport carrier by altering the Kt of glycine influx, but was without significant effect on the amino acid Jmax. 5. The coupling coefficient of mucosal co-transport (JNa/JG) varied with the [Na] being 1-1 at low [Na] (471 mM). 6. A model is proposed in which Na and glycine share ternary (NaXG) and quaternary (Na2XG) carrier complexes during their coupled influxes, but in which glycine may also traverse the mucosal membrane alone by way of an unshared binary (XG) carrier complex.

摘要

对一种海洋虾中肠腔上皮细胞黏膜边界处甘氨酸和钠的流入情况进行了研究。2. 黏膜的甘氨酸流入量（JG）和钠流入量（JNa）均呈现米氏动力学，且每种溶质的流入都明显依赖于浴液中另一种溶质的存在。部分JG在无钠的情况下发生，但JNa似乎完全依赖于甘氨酸。3. 甘氨酸流入的米氏常数（Kt）和最大流入速率（Jmax）依赖于[Na]，而钠流入的Kt和Jmax则依赖于[甘氨酸]。4. 钾通过改变甘氨酸流入的Kt，作为钠与共转运载体结合的竞争性抑制剂，但对氨基酸的Jmax无显著影响。5. 黏膜共转运的偶联系数（JNa/JG）随[Na]变化，在低[Na]（471 mM）时为1 - 1。6. 提出了一个模型，其中钠和甘氨酸在其偶联流入过程中共享三元（NaXG）和四元（Na2XG）载体复合物，但甘氨酸也可能通过未共享的二元（XG）载体复合物单独穿过黏膜膜。