The effect of tributyltin chloride (TBTC) on rainbow trout (Salmo irideus) hemoglo-bin I (HbI) and hemoglobin IV (HbIV) was characterized by the steady-state fluorescence of intrinsic and extrinsic fluorescent probes. The fluorescence emission spectrum (ex 280 nm) is greatly increased in intensity by the presence of the organotin in both proteins. Circular dichroism spectra in the same samples show a small decrease in 222 , a measure correlated with the percentage of the-helical content. Morever, important changes in near-UV, Soret, and visible regions of CD were induced by TBTC. The correlation of data obtained with trout hemoglo-bins (HbI and HbIV) with similar measurements on globins suggests that the presence of heme is necessary for the interaction of the organotin compound with the proteins. Proteins 1999;34:443-452. 1999 Wiley-Liss, Inc.

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In the present work we studied, by chemiluminescence measurements, the influence of lead on the production of reactive oxygen species (ROS) in haemolysates obtained from human erythrocytes incubated in the presence of different concentrations of lead acetate. Moreover, we evaluated the modification of proteins and lipids in human erythrocyte and lymphocyte membranes by using the fluorescence probes N-(1-pyrene)maleimide (PM), laurdan and pyrene. No significant changes in chemiluminescence were detected for erythrocytes incubated with 1-10 microM lead acetate for 3 h at 37 degrees C. By increasing the lead acetate concentration in cell suspensions up to 50 microM for the same incubation time, the percentage of chemiluminescence inhibition was ca. 20%. It was shown that, after incorporating fluorescence probes in the membrane lipid bilayer of erythrocytes and lymphocytes treated with 10 and/or 50 microM lead acetate, the total fluorescence intensity and the excimer to monomer intensity ratio of PM decreased and the generalized fluorescence polarization of laurdan decreased by 10-15%. The pyrene excimerization coefficient (kappa(ex)) increased by 20% (in comparison with a magnitude of kappa(ex) for white membranes isolated from intact erythrocytes) with 6-10 microM lead acetate for 3 h at 37 degrees C. The data obtained suggest that the effect of low concentrations of lead acetate does not cause production of ROS in erythrocytes in vitro, but can change the physicochemical state of proteins and lipids in erythrocyte and lymphocyte membranes. This effect is important because it influences the enzymatic activity and the functionality of receptors and channels present at the plasma membrane level, thus modulating the molecular composition of the intracellular space and cell functions.