INHIBITORY MECHANISM OF LEAD ON TRANSFERRIN-BOUND IRON UPTAKE BY RABBIT RETICULOCYTES - A FRACTAL ANALYSIS

Experimental data of transferrin and transferrin-bound iron uptake by rabbit reticulocytes in the presence or absence of extracellular lead is analyzed by means of a fractal model. A highly significant correlat ion of fractal dimension (Df) of intracellular transferrin or transfer rin-bound iron uptake with varying extracellular concentrations of lea d (0 similar to 25 umol/L) was observed (Transferrin: r = 0.897, p = 0 .015; transferrin-bound iron: r = 0.947, p = 0.004). The Df of membran e-bound transferrin (r 0.618, p = 0.191) or transferrin-bound iron (r = 0.144, p = 0.786) did not appear to be markedly altered by lead. Fur ther analysis shows that inhibitory degree of lead on intracellular ir on uptake is higher than that on intracellular transferrin uptake. The se results suggest that the inhibitory effect of lead on the iron upta ke may occur in intracellular process rather than in membrane binding step, probably inhibiting translocation of iron across the endosomal m embrane.