POSTEXPOSURE PROCESSES IN TEMOPORFIN-PHOTOSENSITIZED CELLS IN-VITRO -RELIANCE ON ENERGY-METABOLISM

The progressive responses to photodynamic treatment (lambda > 590 nm) mediated by Temoporfin have been investigated in vitro on two rodent c ell lines: BHK and murine hepatoma MH22 cells. Comparisons are made of two Light exposure/post-exposure incubation media: Dulbecco's a minim al essential medium (DMEM) and phosphate-buffered saline (DPBS) deplet ed of energy sources. Enhancement of lipid peroxidation is an early re sponse to Temoporfin photosensitization in either experimental set. It is restored to the initial level by subsequent incubation in DMEM, bu t not in DPBS. The decrease in MTT specific activity and especially la ctate dehydrogenase leakage from the cells are faster in DPBS and cont inue to proceed during the post-exposure incubation in the both media. The intracellular ATP pool is completely depleted within 3 h of post- exposure incubation in DPBS, but not in DMEM where, in contrast, an in itial increase in ATP is observed. Based on these preliminary observat ions, it is presumed that ATP synthesized by injured mitochondria and activated glycolysis is being used to restore the deteriorated cell fu nctions and/or to allow reactions involved in apoptosis to proceed. (C ) 1997 Elsevier Science S.A.