The effect of ultrasound on the ionic conductance across frog skin in the presence of free-radical scavengers

In a recent study, Dinno et al. [Ultrasound Meal. Biol. 15, 461–470 (1989).] reported that the increase in ionic conductance across frog skin is primarily due to effects of nonthermal origin. Cavitation was considered to be the major mechanism response for the change in the conductance. Since free radicals (FR), under certain conditions, are known to be generated during cavitation, it was decided to investigate the effect of ultrasound in the presence of free-radical scavengers (FRS). It was found that the presence of 5 mM of either vitamin C or cysteamine caused a significant block to the increase of ionic conductance induced by ultrasound. On the other hand, cystamine, which does not permeate into the cell as readily as the other two FRS, did not interfere as strongly with the action of ultrasound. On the basis of these results, the following indications are suggested: (1) The increase in ionic conductance in the presence of ultrasound is triggered by FR produced by cavitation and (2) in some as-yet-unknown way, secondary effects of cavitation are triggered within the interior of the cell. [Work supported by the NIH under Grant No. 5-RO1-CA-39374-05.]