System y+L-like Activities Account for High and Low Amino-Acid Transport Phenotypes in Chicken Erythrocytes |
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Authors: | M Vargas R Devés |
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Institution: | (1) Programa de Fisiología y Biofísica, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Casilla 70005, Santiago 7, Chile, CL |
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Abstract: | The functional properties of the transport of lysine across the chicken erythrocyte membrane were investigated. The animal
population studied (male Leghorn chickens, 6–14 weeks old) was found to consist of two groups presenting either low (LT, 19
individuals) or high transport rates (HT, 20 individuals). The rates of influx in the two groups, measured at a concentration
of l-lysine of 1 μm, differed by a factor of 34. The transport activities observed in LT and HT erythrocytes were compatible with the general
features of system y+L, but showed some differences in specificity. The transporter in the LT group was found to bind l-lysine, l-leucine, l-methionine and l-glutamine with high affinity, in the presence of sodium, as described for system y+L in human erythrocytes. The activity present in HT erythrocytes exhibited a much lower affinity for l-leucine, but was able to interact strongly with l-glutamine and l-methionine. The specificity pattern of the HT transporter, has not been described in other cell types. In other respects,
the properties of the two systems were similar. Sodium replacement with potassium, drastically reduced the affinity for l-leucine, without affecting lysine transport. Both transporters function as tightly coupled exchangers, are inactivated by
p-chloromercuribenzene sulfonate and resistant to N-ethylmaleimide. These findings explain previous results obtained in selective
breeding experiments of chicken with high and low amino-acid transport activity.
Received: 12 February 2001/Revised: 11 June 2001 |
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Keywords: | : Erythrocytes — Transport — Amino acid — Lysine — Kinetic — Chicken |
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