Potential Use of Radio-labelled Porphyrins for Tumor Scanning
Thaller, R.A., Lyster, D.M., and David Dolphin
Porphyrin Photosensitization Workshop D. Kessel and T.J. Dougherty, Eds. Plenum Press, New York
The synthesis of a variety of metalloporphyrin coordinated to γ-emitting radionuclides is described and the in vitro and in vivo tumor localizing properties were examined in mouse leukemia cell cultures and in carcinoma-bearing rats. Radiolabeled protohemin showed better uptake in the tumor culture cells than hematohemin. Hematohemin uptake was 18.3% of the total activity at 1 h, decreasing to 10.6% at 24 h, and increasing to 12.4% at 72 h. Protohemin had high initial uptake (63.7%) at 3 h, decreasing to 30% at 6 h and then increasing to 87% at 24 h. Radiolabeled meso-tetra(4-N-methylpyridyl)hemin tetraiodide, meso-tetra(4-carboxyphenyl)hemin, and protohemins also showed high initial uptakes in vitro, but poor localizing activity in tumor cells in vivo.