Labelled bleomycin as a tumour-localizing agent. II. The effect of dose loading of the different forms of 57Cobalt-bleomycin A2, B2, and pepleomycin on the tissue distribution and tumour uptake in tumour-bearing rats.

The different forms of 57cobalt-bleomycin (57C0-blm) A2 and B2 as well as 57Co-pepleomycin (57Co-pep), were investigated in tumour-localizing properties of both forms of 57Co-blm are identical if 57Co-blm is injected as a bleomycin solution without carrier cobalt. Differences between the biological behaviour of the various cobalt complexes (which differ in ligand arrangement) were found if these complexes were injected together with inactive cobalt bleomycin complexes of the same form. In this case Co-blm B2 form I and Co-pep form I localize better than Co-blm b2 form II and Co-pep form II respectively. Such a decrease in uptake by the tumour, compared with form I, was not observed for Co-blm A2-II.