Na(+)-dependent L-Alanine and Glycine uptake by rat red blood cells were best fit to a common model of two transport components, saturable transport and diffusion. 24 hours of food deprivation provoked statistically significant increases of the Km and Vmax red cells L-Alanine uptake, whereas the diffusion constant did not change in response to starvation. The Glycine uptake kinetics poorly follows the L-Alanine pattern and no significant response to starvation can be outlined. The physiological meaning of these adaptations has to be related to short term food deprivation regulation, independent of protein synthesis in the erythrocytes. Such mechanisms could be important to account for the previously described changes in the distribution patterns of amino acids between the blood plasma and blood cell compartments in response to short term starvation.