The Comparison of Rotenone and an Environmentally Safe Insecticide (Azadirachtin) on Cultured Cell Respiration

Abstract

Background: Both azadirachtin and rotenone, two botanical pesticides have shown inhibit the growth of cultured insect cells. The inhibitory effect of rotenone on cell growth is through disruption of electron transport chain, but exact mechanism of effect of azadirachtin on growth of cell is unknown. This study was carried out to compare the effect of these phytochemical on oxygen consumption by cultured cells.

Methods: Electron transport and oxygen uptake were measured using the oxygen electrode, which continuously determines the concentration of oxygen in solution. Rotenone was used as a positive control to investigate if azadirachtin had its effect on respiration of the cells. Estimates of oxygen uptake for Sf9 and C6/36 were done at 30°C and for L929 at 37°C.

Results: Preliminary results indicated that concentration of 10⁴ M of azadirachtin had the maximum effect on cell respiration. Also rotenone in concentration of 10^-8 M reduced the cell respiration by 50%. However using purified mitochondria, the effect of azadirachtin on respiration rate was not significant.

Conclusion: Interestingly in present test, both azadirachtin and rotenone could reduce the total oxygen consumption. Azadirachtin had only a minor effect on the respiration rate in both mammalian and insect cultured cells and there was only a slight difference between them. Due to low sensitivity of insect cells and also presence of same sensitivity in mammalian cells it seems that the effect of azadirachtin on cell respiration is different to that of rotenone. Also the results of this study suggest that while cell growth assessment .is not appropriate for all phytochemical pesticides, it is useful for those, such as azadirachtin and rotenone whose effect is on the essential mechanisms of insect cells in general.