Abstract: To investigate the effect of cantharidin (CTD) on insect cell membrane and its mechanism, the cell membrane integrity and potential in Spodoptera frugiperda Sf9 cells treated with CTD were tested by transmission electron microscope (TEM) and laser scanning confocal microscope (LSCM) combined with fluorescent dyes FDA/PI and DiBAC4(3). The results showed that after the Sf9 cells were treated with 32 μmol/L CTD, their membrane structure was not disrupted at 6 h and 12 h after treatment, respectively. The FDA fluorescence intensities of the treated cells evidently declined compared with the control (P<0.05) while the proportion of the PI-staining cells was not significantly different from that of the control (P≥0.05) at 0.5 h after treatment under TEM observations. The membrane potential (MP) in Sf9 cells was depolarized significantly both at 140 s after treatment with 32 μmol/L CTD and in the instantaneous treatment with 64 μmol/L CTD (P<0.05). The MP in Sf9 cells depolarized obviously within 3 h after treatment with 32 μmol/L CTD or 2 h with 64 μmol/L CTD (P<0.05), and then the degree of deplorization declined. At 6 h after treatment with 32 μmol/L CTD or at 3 h with 64 μmol/L CTD, MP deplorization in treated cells was not significantly different from that in the control (P≥0.05). The results suggest that CTD causes the depolarization of cell membrane potential in Sf9 cells, which will maintain for a period of time, and induces an irreversible decline in cell activity, but not destroys the integrity of the cell membrane structure.

Key words: Spodoptera frugiperda, cantharidin, Sf9 cells, membrane integrity, membrane potential;
 depolarization