The photodynamic effects of hematoporphyrin and light on the cytoplasm of human leukemic cells.

Degenerative changes as seen by electron microscopy in malignant cells treated with hematoporphyrin and white light consist of a) swelling and disruption of mitochondria, b) early loss of cytoplasmic projections, c) formation of localized zone of new cytoplasmic projection which then detach from cell surface, and d) nuclear degeneration occurs late as a last event. Therefore, we postulate that the combination of hematoporphyrin and light exerts its primary toxic effects on the cytoplasm and that the first organelle to present morphologic alterations are the mitochondria.