4-acetamido-4--isothiocyanatostilbene-2-2--disulfonic-acid and 2-aminobicyclo(2-2-1)heptane-2-carboxylic-acid

The effects of changes of membrane potential on amino acid transport through systems A, ASC and L was investigated in the Ehrlich cell and the human erythrocyte. Changes of membrane potential were produced by incubating cells whose K+ permeability had been increased, either by valinomycin or by activation of Ca2+-dependent K+ channels, in medium containing different K+ concentrations. The changes in membrane potential were followed by measuring the distribution ratio reached by lipophilic indicators. Transport through Na+-dependent system A was sensitive to the membrane potential, the rate of amino acid uptake increasing 2.2-3.1-times for each 60 mV-hyperpolarization. The Na+-dependent system ASC was insensitive to membrane potential. The Na+-independent system L was not directly affected by membrane potential, but the steady-state accumulation of system L substrates was increased by hyperpolarization.

Topics: 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; Amino Acids; Amino Acids, Cyclic; Animals; Biological Transport, Active; Carcinoma, Ehrlich Tumor; Erythrocyte Membrane; Humans; In Vitro Techniques; Kinetics; Membrane Potentials; Mice; Onium Compounds; Potassium; Propranolol; Sodium; Trityl Compounds