An Examination of the Labelling of Intact Human Erythrocytes with 99mTc

Summary. 99mTc radiopharmaceuticals are now in common use in diagnostic nuclear medicine although rather little is known about the chemical structure of the Tc-ligand complexes formed when Tc is bound to organic compounds. We examine 99mTc-labelled erythrocytes and find that proteins in addition to haemoglobin are labelled with 99mTc, possibly through their sulphydryl groups. This contrasts markedly to the labelling of erythrocytes with 51Cr where only haemoglobin is labelled.