Cobalt chelate of bleomycin. I. Physicochemical properties and distribution in tumor bearing mice.

Abstract

Cobalt chelate of bleomycin (Co-BLM) was inert to ligand exchange reaction and showed absorption at 450 nm and 580 nm, which indicated cobalt is trivalent. Co-BLM was accumulated in tumor tissue much more than BLM and other BLM metal chelates. In urine of 67Ga-BLM or 111In-BLM injected mice, most of radioactivity was not bound to BLM. On the other hand, all the radioactivity was attributable to BLM bound 57Co in urine of 57Co-BLM injected mice. In tumor tissue homogenate, most of Co-BLM was present in cell nuclei, while BLM, CoCl2 and other BLM metal chelates distributed mainly in supernatant fractions. Co-BLM may bind to deoxyribonucleic acid (DNA) in tumor cell. From these results, we conclude Co-BLM to be superior as a tumor scanning agent than BLM and other BLM metal chelates.