Release of lysosomal enzymes and lactate dehydrogenase due to hematoporphyrin derivative and light irradiation of NHIK 3025 cells in vitro.

NHIK 3025 cells in monolayer cultures were irradiated with near ultraviolet light in the presence of hematoporphyrin derivative (HPD). The release of lysosomal enzymes and the cytosol marker enzyme lactate dehydrogenase to the culture medium was determined 1, 3, 6 and 24 hours after irradiation. The enzyme activities of the cell pellet were investigated 24 hours after irradiating the cells. After exposure of HPD-labelled cells to light doses causing no cell inactivation, the leakage of enzymes was slightly inhibited in the first 6 hours followed by a period between 6 and 24 hours when the cells released the same amount or slightly more enzymes than the control. The enzyme activities of cell pellets made 24 hours after exposure were 40-75% of control values due to either a small inhibition of cellular enzyme activity or of inhibited cell growth by this dose. A higher light dose inactivating 80-90% of the cells, caused a rapid release of both lysosomal and cytosol enzymes. The cell pellets contained very little of the enzymes 24 hours after treatment and especially free intracellular enzymes had been released with high efficiency. Leupeptin, a lysosomal protease inhibitor, did not protect the cells from inactivation. We conclude that the release of lysosomal enzymes after porphyrins and light is of little significance in terms of cell killing.