Fig. 5.

Proposed model for effects of endosomal photodamage on endocytosis in 1c1c7 cells. A = A normal membrane recycling pattern. B = Formation of swollen late endosomes when further processing of late endosomes is blocked by wortmannin. C = AlPcS2a labeling pattern. D = Proposed effect of an LD₂₀ light dose on photosensitized endosomes resulting in imperviousness to ‘swollen endosome’ formation. E= Endosomal fragmentation and release of encapsulated AlPcS2a into the cytoplasm after a greater light dose. F = postulated effect of low-dose PDT on cells photosensitized with NPe6. This is based on studies indicating that AlPcS2a targets both lysosomes and late endosomes [14]. Accumulation of photosensitizer is indicated by shading of the organelles;