The role of cavitation in the induction of cellular DNA damage by ultrasound and lithotripter shock waves in vitro.

The induction of DNA strand breaks in Chinese hamster ovary cells was measured with the comet assay after continuous wave ultrasound or lithotripter shock wave exposure. Cell lysis and hydrogen peroxide production were measured to gauge the level of inertial cavitation activity. Significant DNA damage was found after 2.17-MHz ultrasound exposure at 37 degrees C to 0.82 MPa for 2 min or 4 min, and to 0.58 MPs for 4 min. A significant portion of the damage induced at the 0.82-MPa level was repaired by the cells when warmed. Neither exposure to 500 or 1000 shock waves at 37 degrees C in a thin-walled tube, nor exposure to 1000, 1500 or 2000 shock waves at 25 degrees C in a polyethylene pipette bulb produced a significant effect, when the flash of light from the spark-gap discharge was blocked. This finding was consistent with the generally lower lysis and hydrogen peroxide production by the shock wave exposure.