Mechanism of the localization of manganese (III) mesotetra(4-sulfonatophenyl)porphine i in mice bearing L1210 tumors

In accordance with earlier work the manganese (III) derivative of meso-tetra-(4-sulfonatophenyl)porphine (TPPS₄) is found to accumulate in the tumors of L1210-bearing mice. The tumor/liver ratio of porphyrin extends from 1.5 to 3.6 over a range of dose and time periods. The subcellular distribution of porphyrin in L1210 tumor and liver, and the tissue distribution (cellular, stromal, soluble) in L1210 tumor indicates that the porphyrin tends to be located predominantly in soluble and stromal fractions. These data are interpreted in terms of the physiology and composition of neoplastic tissue to formalize a mechanism for the localization of Mn(III)TPPS₄ in L1210 tumor and a general working hypothesis for the localization of porphyrins in neoplastic tissue. The in vivo stability of Mn(III)TPPS₄ is also addressed and is found to be demetallated to a degree of approximately 1% in liver and kidney.