| Abstrakt: |
Several recent articles on labelling of red blood cells with 99Tcm(Ducassou et al., 1976; Smith and Richards, 1976) have reported labelling efficiencies without reference to the method or methods by which these yields were obtained. It has been shown (Dewanjee, 1974) that the 99Tcmwhich is strongly bound to the red blood cells (RBC) is associated with the haemoglobin, but the intrinsic membrane protein and sialoglycoprotein and the traces of plasma proteins which adhere non-specifically to the cell surface could also react with 99Tcmin the presence of tin (Sn+2). These latter potential reactants probably represent 99Tcmthat is weakly bound to the RBC. In addition, unreacted 99Tcm(VII) or colloid-reduced and hydrolyzed 99Tcmcould also be presented in the reaction mixture. Instant thin-layer chromatography (ITLC), paper chromatography (PC) or the centrifuge assay system could be adapted to give estimates of the degree of dissociation of 99Tcmfrom the RBC but all these methods have disadvantages because of the nature of the labelled preparation. An ITLC or PC system, using an alcoholic solvent, would tend to overstate the labelling yield because only 99TcmO4-would be detected and quantitated. The centrifuge assay requires a five to ten-minute centrifugation and one or two washes to effect complete separation of unbound 99Tcmfrom that bound to cells; in this case the labelling yield could be understated because excessive cell washings could induce lysis and/ or leakage of label from the cell. |
