title: Changes in amino acid influx with Na flow in incubated slices of mouse brain.
abstract: The uptake of amino acids into slices of adult and newborn mouse brain was studied in relation to Na+ flow. (1) The level of Na+ and K+ incubated slices of brain depends on the ionic composition of the incubation medium. The intracellular levels of Na+ in adult tissue are below, in fetal tissue above, Na+ levels in the medium used. Rapid net flow into or out of the tissue can be achieved by transferring slices into media of higher or lower Na+ content. (2) Under conditions of net Na+ inflow, the influx of all amino acids tested increased; under conditions of net Na+ outflow, the influx of all amino acids decreased, as compared to slices in ionic equilibrium. The absolute levels of Na+ in the tissue under the experimental conditions had little effect on amino acid uptake. The stimulatory effect of Na+ inflow and the inhibitory effect of Na+ outflow could be observed at all developmental stages--in adult, newborn, and fetal tissue. (3) We conclude that ion movements influence metabolite transport; these effects are smaller in the absence of fully developed ion pumps. The direction of the net ion flow does not seem to be the main determinant: active accumulation occurred both in adult and in fetal brain, although the tissue-to-medium Na+ gradients were in opposite directions; in addition, amino acid inflow occurred in the presence of Na+ outflow.
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D001692:Biological Transport; D001921:Brain / Q000201:enzymology / Q000378:metabolism*; D066298:In Vitro Techniques; D051379:Mice; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D012964:Sodium; D011188:Potassium