Thiamin transport by human erythrocytes and ghosts.

摘要: Thiamin transport in human erythrocytes and resealed pink ghosts was evaluated by incubating both preparations at 37 or 20°C the presence of [3H]-thiamin high specific activity. The rate uptake consistently higher than ghosts. In preparations, time course independent from Na+ did not reach equilibrium after 60 min incubation. At concentrations below 0.5 μm 37°C, thiamin taken up predominantly a saturable mechanism Apparent kinetic constants were: for erythrocytes,Km=0.12, 0.11 0.10 andJmax=0.01, 0.02 0.03 pmol·μl−1 intracellular water 3, 15, 30 incubation times, respectively; ghosts,Km=0.16 0.51 andJmax=0.01 0.04 15 respectively. 20°C, component disappeared preparations. Erythrocyte influenced ofd-glucose metabolic inhibitors. inhibited competitively unlabeled thiamin, pyrithiamin, amprolium and, to lesser extent, oxythiamin, inhibiting effect being always more marked Only approximately 20% protein-(probably membrane-) bound. A similar proportion esterified pyrophosphate. Separate experiments using valinomycin SCN− showed that which is cation pH 7.4, unaffected changes membrane potential