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 determinedin Allium cepa meristematic cells. Both photosensitizers (10^–7M for 4 h) penetrated into the nucleus producing a red fluorescenceof chromatin under blue-violet (436 nm) exciting light. Theability of T₄MPyP and ZnT₄MPyP to induce DNA photodamage wasmeasured by the sister chromatid exchange (SCE) test. 5-Bromo-2'-deoxyuridine-substitutedchromosomes treated with both the porphyrins (10^–8 M for4 h) showed increased frequencies of SCE when they were postirradiatedwith 436 nm light. A higher genotoxic effect was observed forZnT₄MPyP than the other compound. ¹To whom correspondence should be addressed