Quantitative analysis of intracellular behaviour of porphyrins.

Fluorometric analysis performed on L 1210 cells after treatment with Photofrin indicated that the interactions with cellular structures induce a significant modification of the equilibria among the different porphyrin species. This modification turned out to be dependent on the uptake and release processes. Thus, a comparative analysis of the dynamic aspects of the drug accumulation process was performed on cells treated with hematoporphyrin, Photofrin and Photofrin II. The results obtained were interpreted taking into account the different chemical composition of the drugs employed. The porphyrin species mainly released seem to be the monomeric ones and 'unfolded oligomers'. The release process results in further modifications of the aggregation and/or configu-rational state of intracellular porphyrins due to altered internal equilibrium.