Abstract
The Na+-independent uptake of l-alanine has been studied in trout red blood cells, isolated hepatocytes and peripheral blood lymphocytes. The present study shows the existence of two functionally different Na+-independent systems for short chain neutral amino acids in these cells. They are designated as asc systems because of their resemblance to systems described in other cell types. Besides their independence of sodium and a rough similarity in substrate preference, the most important property shared by the two carriers is a lack of trans-stimulation, allowing further differentiation from system L. One of them is an unusually stereospecific carrier present in red blood cells, the other is less restrictive and present in hepatocytes and peripheral blood lymphocytes. Extracellular acid pH increases the incorporation to red blood cells, while it slightly depresses the uptake in the other cells. From the data presented, it is not possible, at first, to classify these carriers as asc 1 or asc 2 systems. Moreover, the system present in red cells resembles that found in the nonerythroid cells, BSC-1, while there is no clear parallelism between the system found in hepatocytes/lymphocytes and any of those described previously.
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References
Barker, G.A., Ellory, J.C. 1990. Review article: The identification of neutral amino acid transport systems. Exp. Physiol. 75:3–26
Ballatory, N., Boyer, J.L. 1988. Characteristics of l-alanine uptake in freshly isolated hepatocytes of elasmobranch Raja erinacea. Am. J. Physiol. 254:R801-R808
Borghetti, A.F., Kay, J.E., Wheeler, K. 1979. Enhanced transport of natural amino acids after activation of pig lymphocytes. Biochem. J. 182:27–32
Canals, P., Gallardo, M.A., Blasco, J., Sánchez, J. 1992. Uptake and metabolism of l-alanine by freshly isolated trout (Salmo trutta) hepatocytes: the effect of fasting. J. Exp. Biol 169:37–52
Christensen, H.N. 1989. Distinguishing amino acid transport systems of a given cell or tissue. Methods Enzymol. 173:576–616
Fincham, D.A., Ellory, J.C., Young, J.D. 1992. Characterization of a novel variant of amino acid transport system asc in erythrocytes from Przewalski's horse (Equus przewalskii). Can. J. Physiol. Pharmacol. 70:1117–1127
Fincham, D.A., Mason, D.K., Young, J.D. 1985. Characterization of a novel Na+-independent amino acid transporter in horse erythrocytes. Biochem. J. 227:13–20
Fincham, D.A., Wolowyk, M.W., Young, J.D. 1990. Characterisation of amino acid transport in red blood cells of a primitive vertebrate, the Pacific hagfish (Eptatretus stouti). J. Exp. Biol. 154:355–370
French, C.J., Mommsen, Th.P., Hochachka, P.W. 1981. Amino acid utilisation in isolated hepatocytes from rainbow trout. Eur. J. Biochem. 113:311–317
Gallardo, M.A., Planas, J., Sánchez, J. 1992. l-serine uptake by trout (Salmo trutta) red blood cells: the effect of isoproterenol. J. Exp. Biol. 163:85–95
Gallardo, M.A., Sánchez, J. 1993. Glycine uptake by trout (Salmo trutta) red blood cells. J. Membrane Biol. 134:251–259
Houston, A.H., McCullough, C.A.M., Keen, J., Maddalena, C., Edwards, J. 1985. Rainbow trout red cells in vitro. Comp. Biochem. Physiol. 81A:555–565
Kuhlmann, M.K., Vadgama, J.V. 1991. Characterization of threonine transport into a kidney epithelial cell line (BSC-1). Evidence for the presence of Na+-independent system asc. J. Biol. Chem. 266: 15042–15047
Norman, P.S.R., Mann, G.E. 1987. Ionic dependence of amino-acid transport in the exocrine pancreatic epithelium: calcium dependence of insulin action. J. Membrane Biol. 96:153–163
Vadgama, J.V., Castro, M., Christensen, H.N. 1987. Characterization of amino acid transport during erythroid cell differentiation. J. Biol. Chem. 262:13273–13284
Vadgama, J.V., Christensen, H.N. 1985. Discrimination of Na+-independent transport systems L, T, and ASC in erythrocytes. Na+ independence of the latter a consequence of cell maturation: J. Biol. Chem. 260:2912–2921
Young, J.D., Ellory, J.C. 1977. Substrate specificity of amino acid transport in sheep erythrocytes. Biochem. J. 162:33–38
Young, J.D., Mason, D.K., Fincham, D.A. 1988. Topographical similarities between harmaline inhibition sites on Na+-dependent amino acid transport system ASC in human erythrocytes and Na+-independent system asc in horse erythrocytes. J. Biol. Chem. 263: 140–143
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This work was supported in part by a grant from the DGICYT (PB91-0235) of the Spanish Government and by a grant from the CIRIT (AR91-21) of the Generalitat de Catalunya. M.A.G. is a recipient of a fellowship from the Generalitat de Catalunya. We would like to express our sincere thanks to Mrs. Rosa Marsol and Mr. Antonino Clemente (Medi Natural, Generalitat de Catalunya) for their help and logistical assistance and to Mr. Robin Rycroft for his editorial help. J.L. Albi, P. Canals and M.A. Gallardo contributed equally to this study.
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Albi, J.L., Canals, P., Gallardo, M.A. et al. Na+-independent l-alanine uptake by trout cells. Evidence for the existence of at least two functionally different asc systems. J. Membarin Biol. 140, 189–196 (1994). https://doi.org/10.1007/BF00233707
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DOI: https://doi.org/10.1007/BF00233707