The inhibition of ascitic S180 and induced sarcoma 180 in vivo was studied with the combination of hematoporphyrin derivatives (HpD) and ultrasound (US) at the frequency of 1.1 MHz and different intensities by light microscopy observation, electronic microscopy observation, cytochemical analysis and fluorescence labeling. The present study indicated that the injury of as-citic S180 increased as time passed and the inhibitory effect was stronger in US plus HpD group than that in other groups. Our results also indicated that the changes in cell structure, cytochrome C oxidase activity, the degradation and missing of DNA were the important factors that inhibited the tumor cell growth and even induced cell death. The phenomenon of apoptosis of tumor cells indicated that cell death and induced apoptosis exist in the treatment of sonodynamic therapy (SDT). Our study investigated the mechanism underlying the killing effect of S180 induced by US activating HpD by the observation of cell morphology and dynamic changes from seminal injury to succeeded injury even to death. It would provide rich reference for the study of SDT.
