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 correlation of fractal dimension (Df) of intracellular transferrin or transferrin-bound iron uptake with varying extracellular concentrations of lead (0 approximately 25 umol/L) was observed (Transferrin: r = 0.897, p = 0.015; transferrin-bound iron: r = 0.947, p = 0.004). The Df of membrane-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. Further analysis shows that inhibitory degree of lead on intracellular iron uptake is higher than that on intracellular transferrin uptake. These results suggest that the inhibitory effect of lead on the iron uptake may occur in intracellular process rather than in membrane binding step, probably inhibiting translocation of iron across the endosomal membrane.