INTRACELLULAR CALCIUM DYNAMICS DURING PHOTOLYSIS

The objective of this investigation was to gain a deeper understanding of the intracellular events that precede photolysis of cells. A model system, consisting of malignant melanoma cells pretreated,vith the ca lcium sensitive fluorescent dye, Fluo-3, was used to examine the intra cellular calcium dynamics in single-cell photolysis experiments. Expos ure of the cells to 632 nm laser light in the presence of photosensiti zer, tin chlorin e6, resulted in a rise in intracellular calcium. The increase in intracellular calcium,was blocked using a variety of calci um channel blocking agents, including verapamil, nifedipine, and nicke l. Treatment with the channel blockers was also effective in either de creasing or eliminating cell death despite the presence of lethal dose s of photosensitizer and irradiation. These results show that intracel lular calcium rises prior to plasma membrane lysis, and that this earl y rise in intracellular calcium is necessary for membrane rupture.