Embryotoxicity of TPPS4 and PS 3 photosensitizers in chicken embryo under different fight conditions

Hematoporphyrin derivatives have been recommended for photodynamic therapy of malignant processes. We administered TPPS4, and Photosan 3 (PS 3) in chi ck embryo in ovo, with or without subsequent blue light (400-550 nm) irradi ation. The aim was to analyze and compare the effects of both substances on organogenesis under different light conditions. The embryotoxic effect (em bryonic death and malformations) was detected after a single intra-amniotic injection of 5 different doses (0.3 to 300 mug) of TPPS4 or PS 3 at embryo nic day 3-5. The beginning of the embryotoxicity range (minimal embryotoxic : dose) was determined in non-irradiated embryos to be between 0.3-3.0 mug PS 3 and 3.0-30.0 mug TPPS4. Malformations of surviving embryos were simila r after both substances, represented by trunk hyperlordosis combined with i ncomplete closure of the ventral body wall and protrusion of viscera as con sequences of amnion contraction, reduction limb deformities, eye malformati ons and cleft beak. Ten minutes light irradiation in ovo following two hour s after intra-amniotic injection of TPPS4 or PS 3 increased by one order of magnitude their embryotoxic effects. Even dark-ineffective doses became hi ghly embryotoxic. Contraction of the amniotic sac and extraembryonic vessel s seemed to be a common mechanism of photosensitizer action.