Effects of pH changes on systems ASC and B in rabbit ileum
Munck, B.G.; Munck, L.K.
American Journal of Physiology 276(1): G173-G184
1999
ISSN/ISBN: 0002-9513 PMID: 9886993 Document Number: 503609
Influx of D-aspartate ( D-Asp), L-glutamate ( L-Glu), and serine (Ser) across the brush-border membrane of the intact mucosa from rabbit ileum has been examined. L-Glu influx is chloride independent and completely sodium dependent. D-Asp and L-Glu share a transport system with a maximum transport rate of 1 mmol.cm-2.h-1 and an apparent affinity constant (K1/2) of 50% of Ser influx at pH 7.2. The remaining 50% can be ascribed to system B. Transport of Ser by system B is reduced by >95% at pH 5.65. At pH 7.2 Ki of Ser against transport of leucine (Leu) by system B is 18 mM and Ki of Leu against transport of Ser is 1.7 mM. The low-affinity transport of L-Glu and the L-Glu-sensitive transport of Ser are performed by an equivalent of system ASC. Supplementary experiments using the jejunum confirm the validity of these results for a major portion of the rabbit small intestine. Reprinted by permission of the publisher.