Influence of dissolved gases on chemical and biological effects of ultrasound.

The influence of dissolved gases (O2, Ar, N2O, and CO2) on the chemical and biological effects of 1.2 MHz continuous wave ultrasound was investigated. Spin-trapping of OH and H radicals with 5,5-dimethyl-1-pyrroline 1-oxide (DMPO) and observation of iodine liberation from a potassium iodide-starch solution were employed for monitoring the chemical effects, while lysing of mouse L5178Y cells was employed for monitoring the biological effects. The effectiveness of the dissolved gases in producing OH-DMPO adducts and H-DMPO adducts was O2 greater than Ar greater than N2O = CO2 approximately equal to O and Ar greater than O2 = N2O = CO2 approximately equal to O, respectively. A result similar to the yield of OH-DMPO was obtained from the liberation of iodine induced by ultrasound. In addition, the effectiveness of the dissolved gases in lysing mouse L5178Y cells by ultrasound was O2 = Ar greater than N2O = CO2 approximately equal to O. These results suggest that both dissolved N2O and CO2 gases in solution suppressed not only the chemical effect but also the biological effect.