Primary effects of singlet oxygen sensitizers on eggs and embryos of sea urchins

Photodynamic effects of rose bengal, a well-known singlet oxygen sensitizer, and of haematoporphyrin derivative, the most widely used sensitizer in photodynamic therapy of tumours, could be visualized using sea urchin eggs and embryos. This biological material is a valuable model for the analysis of mechanisms and/or sites of the photodynamic action occurring in any living tissue. Depending on the sensitizer used, singlet oxygen may be identified as the main mediator of the cytotoxic effects observed. Besides observations made on the living, in particular within the context of fertilization ability of the egg cell, gross damages of the cells are morphologically analysed by scanning electron microscopy. The results support the working hypothesis explaining the different susceptibility of healthy and tumour cells for photosensitization as a cell cycle phenomenon.