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AJP - Regulatory, Integrative and Comparative Physiology, Vol 255, Issue 4 648-R653, Copyright © 1988 by American Physiological Society
ARTICLES |
S. Vilella, G. A. Ahearn, G. Cassano and C. Storelli
Dipartimento di Biologia, Universita' di Lecce, Italy.
L-[3H]proline uptake by brush-border membrane vesicles prepared from intestinal mucosa of the European eel, Anguilla anguilla, was stimulated by a transmembrane Na gradient (out greater than in). Kinetic analysis of L-proline influx, under short-circuited membrane potential conditions, indicated the presence of an apparent single Na-dependent carrier process (Kapp = 0.23 +/- 0.04 mM and Jmax = 7.96 +/- 0.87 nmol.mg protein-1.min-1) and a nonsaturable transfer component with an apparent diffusional permeability (P) of 1.53 +/- 0.35 microliter.mg protein-1.min-1. An imposed transmembrane potential (inside negative) increased apparent L-proline binding affinity (lowered Kapp) without appreciably altering maximal amino acid influx (Jmax). Hill analysis of L-proline influx over a wide range of external Na concentrations indicated a 1:1 stoichiometry for Na-proline cotransport. Use of amino acid inhibitors of L-proline influx suggested that L-proline transfer may occur by either a classical Na-dependent A System with a wide substrate specificity or by the combination of Na-dependent PHE (phenylalanine preferring) and IMINO (proline, alpha-methylaminoisobutyric acid preferring) Systems.
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L. Ingrosso, S. Marsigliante, V. Zonno, C. Storelli, and S. Vilella An L-proline-dependent proton flux is located at the apical membrane level of the eel enterocytes Am J Physiol Regulatory Integrative Comp Physiol, November 1, 2000; 279(5): R1619 - R1624. [Abstract] [Full Text] [PDF] |
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