Uptake and DNA photodamage induced in plant cells in vivo by two cationic porphyrins.

The in vivo uptake of two cationic porphyrins: mesotetra (4-N-methylpyridyl) porphine (T4MPyP) and its zinc complex (ZnT4MPyP) was determined in Allium cepa meristematic cells. Both photosensitizers (10(-7) M for 4 h) penetrated into the nucleus producing a red fluorescence of chromatin under blue-violet (436 nm) exciting light. The ability of T4MPyP and ZnT4MPyP to induce DNA photodamage was measured by the sister chromatid exchange (SCE) test. 5-Bromo-2'-deoxyuridine-substituted chromosomes treated with both the porphyrins (10(-8)M for 4 h) showed increased frequencies of SCE when they were postirradiated with 436 nm light. A higher genotoxic effect was observed for ZnT4MPyP than the other compound.