In vivo experimental studies on the role of free radicals in photodynamic therapy. III. Photodynamic effect on free radicals generated in cell cultures.

The effect of excited Photofrin II molecules on the zymosan stimulated and luminol dependent chemiluminescence (CL) of macrophages, known as respiratory burst, has been studied. Excitation was carried out by light irradiation in the vicinity of the maximal CL by varying light doses. In separate experiments potassium salt of 3,5-di-tert-butyl-4-hydroxyphenyl propionic acid radical inhibitor was added to the system and its consumption measured spectroscopically. Based on the experimental results the decrease in the steady state radical concentrations under the influence of radical inhibitor and of triplet sensitizer generated in situ has been calculated. It has been established that the corresponding photodynamic effect is an inhibition-like process proceeding by triplet-doublet interactions.