Mouse skin photosensitization with benzoporphyrin derivatives and Photofrin: macroscopic and microscopic evaluation

A comparative study, at both the macroscopic and microscopic level, of skin photosensitivity caused by four isomeric forms of benzoporphyrin derivative (BPD) has been carried out, and compared to effects of Photofrin. Animals injected intravenously with BPD analogues and exposed to light 3 h later showed extensive photosensitivity. Animals receiving the monoacid derivatives of BPD (BPD-MA and BPD-MB) showed markedly more photosensitivity than those receiving the diacid derivatives (BPD-DA and BPD-DB). Animals receiving BPD analogues which were exposed to light 24 h or more later showed only minimal reactivity. Histological examination of biopsies taken after photosensitizer injection and light exposure showed extensive changes in epidermis and dermis, including epidermal erosion, degranulation of the stratum granulosum, spongiosis, depletion in cellularity and mast cell degranulation. These changes were noted to be similar to changes caused by Photofrin.