Photochemistry and photobiology
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Photochem. Photobiol. · Apr 1999
Analysis of pulmonary microvasculature changes after photodynamic therapy delivered to distant sites.
Photodynamic therapy (PDT) can exert local damage by direct tumor cytotoxicity, by disruption of the microvasculature or by a combination of these effects. Although systemic effects after PDT of small tissue areas (< 1% total body surface area) are unlikely, treatment of larger areas may result in an accumulated effect leading to toxicity. Several investigators have described animal death after high dose PDT to tumors on the hind limb of animals and hypothesized that a toxic shock syndrome caused by vasoactive agents released after PDT is responsible. ⋯ The progression of pulmonary edema was assessed by monitoring the leakage of rhodamine-labeled albumin and by wet-to-dry lung weight ratios. Although an increased leukocyte adherence was observed and a significant number of animals died after the extensive PDT treatment, no biologically significant lung edema could be demonstrated. These data indicate that lung edema and acute respiratory distress syndrome is not the cause of death in these animals and that the toxicity is related to other mechanisms including circulatory shock after extensive muscle damage.