Modulation of 5-ALA-induced PpIX xenofluorescence intensities of a murine tumour and non-tumour tissue cultivated on the chorio-allantoic membrane

Abstract

Exogenous administration of 5-aminolaevulinic acid (5-ALA), an early precursor in haem synthesis, induces accumulation of endogenous photo-active porphyrins, particularly protoporphyrin IX (PpIX). Modulation of 5-ALA-induced PpIX-xenofluorescence intensities of a murine tumour and normal (non-tumour) tissue was studied in vivo on the chorio-allantoic membrane (CAM) of fertilized chicken embryos. Tumours were grown from the murine fibrosarcoma cell line SSK II. Murine 3T3 fibroblasts (clone A31) were used for cultivating normal tissue. The autofluorescence and xenofluorescence intensities of 5-ALA-induced PpIX xenofluorescence were compared. After administration of 5-ALA to the CAM inoculated tissues, the SSK II tumours exhibited higher xenofluorescence intensities than the 3T3 tissues. Autofluorescence intensities of both types of tissue were not distinguishable. The effects of several biochemical reagents on the xenofluorescence intensities of the fibrosarcoma and fibroblast tissues were investigated. In both tissue types, the intensities increased after incubation with glucose and antimycin A, while nicotine-adenine-dinucleotide increased the 3T3 fibroblast xenofluorescence more than the SSK II fibrosarcoma xenofluorescence. Incubation with dimethyl sulphoxide (DMSO) attenuated 5-ALA-induced PpIX xenofluorescence, while oxamic acid attenuated the 3T3 fibroblast xenofluorescence more effectively than the xenofluorescence of SSK II fibrosarcoma. Ethanol and 2-iodoacetamide drastically decreased xenofluorescence intensities in both tumour and normal tissue.