Effect of lead on physical state of erythrocytes and model membranes.

Lead has an high affinity for erythrocyte and influences the membrane bound enzymes activities but its interactions with biological membranes is still unclear. We have investigated the effect of lead as free ion on physical state of erythrocytes and liposomes by Electron Spin Resonance (ESR) using two spin labels 5-doxyl-stearate (5-NS) and 16-doxyl-stearate (16-NS) and by DPH (1,6-diphenyl-1,3,5-hexatriene) fluorescence polarization analysis. Lead induces decrease of fluidity in natural membrane which is more evident in membrane hydrophobic core; the effect is not correlated with lead concentration. Lead ion interacts with negative charged liposomes inducing an increase of their microviscosity.