title: Stimulation of leucine transport by a mitogen through intracellular Ca2+ increase in human peripheral lymphocytes.
abstract: The effect of concanavalin A and ionophore A23187 on leucine uptake by human peripheral lymphocytes has been examined. Preincubation of the cells with 32 micrograms/ml concanavalin A or 0.1 microM A23187 increased leucine uptake by 67% and 100%, respectively. Both concanavalin A and A23187 could, within 2 min, induce a more than 2-fold increase in the cytoplasmic free Ca2+ concentration ([Ca2+]i). This increase by concanavalin A was completely blocked by the addition of 0.1 mM 8-(N,N-diethylamino)-octyl-3,4,5-trimethoxybenzoate (TMB-8) to incubation medium; TMB-8 partially blocked the action of A23187. The stimulation of leucine uptake by concanavalin A and A23187 was strongly inhibited by the presence of TMB-8 in the medium, whereas the basal uptake was not affected by this intracellular Ca2+ antagonist. Amiloride did not inhibit the stimulation of leucine uptake by concanavalin A. The concanavalin A- and A23187-induced elevation of [Ca2+]i was accompanied by membrane hyperpolarization. Concanavalin A-stimulated leucine uptake was greatly inhibited by the presence of an excess of 2-aminobicyclo[2.2.1]heptane-2-carboxylic acid. These results indicate that the increase in [Ca2+]i may function as a signal of the stimulation by mitogen of leucine uptake mediated by system L, finally inducing membrane hyperpolarization in human lymphocyte.
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D000001:Calcimycin / Q000494:pharmacology*; D002118:Calcium / Q000032:analysis / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002478:Cells, Cultured; D003208:Concanavalin A / Q000494:pharmacology*; D003593:Cytoplasm / Q000032:analysis; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D007930:Leucine / Q000493:pharmacokinetics*; D008214:Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials
chemical_list: D002121:Calcium Channel Blockers; D003208:Concanavalin A; D000001:Calcimycin; C006014:8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate; D005707:Gallic Acid; D000584:Amiloride; D007930:Leucine; D002118:Calcium