Lithotripter shock waves are capable of damage at sub-cellular dimensions in the absence of cavitation

Abstract

Lithotripter shock waves (SW’s) cause tissue damage, but the size dimension of the SW-tissue interaction is not known. Unilamellar membrane vesicles were used as a model for subcellular organelles, and SW-induced damage was quantitated with and without cavitation. Membrane vesicles (≊100 nm diameter) were made by extrusion from egg phosphatidylcholine, and exposed to SW’s (1 Hz and 20 kV) in a research lithotripter that yields output similar to an unmodified Dornier HM3. SW-dependent vesicle lysis was linearly dependent on SW number (p<0.001), with a mean lysis of 0.12±0.02% at 400 SW’s (n=49 vials). This lysis value is >100 times less than that seen in red blood cells exposed to a similar SW dose. Vesicle lysis was independent of kV in the range tested (17–23 kV, p>0.9, n=14 vials). When vesicles were exposed to SW’s in the presence of high overpressure (>130 atm) to eliminate cavitation effects, SW’s still induced lysis not different from that at atmospheric pressure, 0.10±0.02% (n=10). This implies that lithotripter shock waves may be capable of causing intracellular damage to tissue even in regions where cavitation does not occur. [Work supported by NIH Grants P01 DK43881 and R01 DK55674.]