Effect of doxorubicin on actin reorganization in Chinese hamster ovary cells.

Exposure of Chinese hamster ovary (CHO AA8) cells to doxorubicin in doses of 75 microM resulted in reorganization of F-actin filaments and characteristic feature of apoptosis. Even increase in size of CHOAA8 cells was observed. Attached cells become more flattered and elongated than control ones. Intense labeling of F-actin around the nucleus and disrupted filaments in cytoplasm as well as stress fibres and bundles of F-actin were seen. Cells detached were rather rounded and there were not stress fibres present. In these cells the network of F-actin was weak and rather disrupted and cells with buds labelled for F-actin were observed. In section from confocal microscopy labeling of F-actin in nucleus was confirmed. Electron microscopy showed cells with multisegmented nuclei. Cells with intracellular area with small and large vacuoles and containing also electron-dense material were seen. Other cellular organelles were rather well preserve. There were margination and condensation of chromatin in nucleus. Immunogold labelling of actin was observed in cells whether or not treated with doxorubicin. Positivity for actin was localized in the nuclei and cytoplasm. In the nucleus gold particles were localized predominantly in the area of condense chromatin. Positive labeling for actin was not found after control incubation. These findings show that doxorubicin promotes changes in the distribution of actin in CHOAA8 cells and that reorganization of actin in these cells is involved in process of apoptosis.