Ultrastructure Localization of Tri-n-Butyltin in Human Erythrocyte Membranes during Shape Transformation Leading to Hemolysis

Scanning electron microscopy, transmission electron microscopy, freeze-fracture and x-ray energy dispersive spectrometry were used to localize tri-n-butyltin (TBT) in human erythrocytes (RBC's). TBT induced a rapid shape transformation of the RBC discocyte to an echinocyte, which led to hemolysis at concentrations at or above 10 micrometers TBT. Electron dense spheres or ellipsoids were observed in association with blood cell membranes at or above 10 micrometers TBT. These structures were visualized initially in thin sections when postfixed with osmium tetroxide. Control cell preparations without TBT did not exhibit these structural densities when fixed with osmium. Freeze-fracture replicas confirmed the presence of TBT aggregates associated with cell membranes as intercalations in the lipid bilayer. In this sections, these structures measured 71.5 + or - 18.2 nm in diameter. In freeze-fraction replicas of TBT-treated RBC's, particulate structure measuring 60+ or -18.5 nm in diameter were present on membrane exoplasmic fracture faces and 59.6+ or - 10.8-nm depressions on membrane protoplasmic fracture faces. Qualitative x-ray energy dispersive spectrometry analysis of ultrathin sections of glutaraldehyde-carbohydrazide-embedded samples revealed that the membrane-associated aggregates contained tin. TBT-treated RBC's that were washed with normal saline resulted in a paucity of TBT aggregates associated with the membranes and a reduction in the RBC hemolysis rate. RBC shape transformation occured at each concentration examined from 0.1 to 100 micrometers TBT, but was reversible below 1 micrometer TBT.