Embedding of radiographic media molecules in the membrane of erythrocytes

The incubation of erythrocytes (RBC) or endothelial cells (HUVEC) in radiographic contrast media (RCM) could induce morphological alterations of or at the cell membranes, e.g. the generation of echinocytes or the formation of stress fibres coinciding with a massive buckling of HUVEC into the vascular lumen, as was demonstrated in several examinations in the recent years. The apposition or embedding of RCM at or in the cell membranes was discussed as possible causative mechanisms because the embedding of molecules into the internal leaflet of the cell membrane bilayer is expected to bulge the cell membrane to the outside, thus inducing e.g. the generation of echinocytes. The examination presented here is based therefore on high resolution scanning electron microscopy (SEM) analyses if iodine as marker element of RCM molecules can be found near the inside of or in RBC membranes (co-localisation study). Morphological analyses exploited secondary electron images (SE) while the analysis of elements exploited either back scattered electrons (BSE) or energy dispersive X-ray analysis (EDX) or the areal display of elements in high lateral resolution in the Bit-map modus. Even at the highest convenient magnification (1:40,000) it was impossible to detect RBC membrane associated iodine (I) after RBC incubation in RCM (Iodixanol, Iopromide) in vitro. Neither in the birds view on the samples nor looking from the side on the freeze fractured samples carrying the RBC was it possible to detect either the signal cohorts typical of I in the sum spectra or the main Lα1-peak in trace analysis.