MORPHOLOGICAL ASPECTS OF AN EXPERIMENTAL TUMOR PHOTOSENSITIZED WITH AMESOSUBSTITUTED CATIONIC PORPHYRIN

The meso-substituted cationic porphyrin, meso-tetra(4N-methyl-pyridyl) porphine (T(4)MP(y)P) appears to be a selective tumour localizer on th e basis of pharmacokinetic studies. Irradiation (at 600-680 nm) of an intramuscularly implanted MS-2 fibrosarcoma in Balb/c mice at 24 h aft er injection of T(4)MP(y)P causes tumour necrosis: histological and ul trastructural analyses of tumour specimens taken at different times af ter phototherapy indicate slowly-appearing tissue damage which involve s both malignant cells and the vascular endothelium. At the subcellula r level, the membranous systems and nuclei are the main targets of the photoprocess. The tumour necrosis is particularly extensive upon inje ction of 4.1 mg kg(-1) T(4)MP(y)P.