Influence of dissolved and free gases on iodine release and cell killing by shock waves in vitro.

Exposure of a potassium iodide solution to lithotripter shock waves resulted in formation of iodine with the amount of iodine depending on the gas dissolved in the solution. Iodine yield was higher with O2 and Ar, as compared to CO2 and N2O; degassed solution revealed the lowest iodine yield. Exposure of L1210 mouse leukemia cells to shock waves reduced the number of viable cells with no difference between O2-, Ar-, or N2O-equilibrated and degassed conditions. CO2 equilibration resulted in a more pronounced reduction. The difference between chemical and biological effects argues against the involvement of free radicals in cell killing by shock waves. In additional experiments, gas bubbles of various sizes were introduced into the test vials. Addition of a 10 microL gas bubble revealed an over 10-fold increase in iodine yield from degassed potassium iodide solution with all gases. Addition of a gas bubble also reduced the number of viable cells again with no difference between the gases. It is suggested that shock wave-gas bubble interaction is an important mediator of iodine release and cell killing by shock waves.