Effect of ultrasound on the contraction of isolated myocardial cells of adult rats

Enzymatically isolated myocardial cells of Wistar rats were used to study contraction under the influence of ultrasound. The dynamics of sarcomere length were measured using a laser diffraction technique. The presence of continuous-wave ultrasound ( f = 2.25 MHz, p spta = 0.3 MPa and f = 10 MHz, p spta = 0.15 MPa) did not cause any significant change in sarcomere dynamics ( n = 21). However, it was shown that stimulation threshold could be decreased when ultrasound at 10 MHz was applied (14 of 22 cells). Low-frequency ultrasound was not able to cause these alterations. This effect was also found to be dependent on the distance between the sound transducer and the cells. Since temperature effects were negligible and cavitation was very unlikely under the given experimental conditions, we propose that acoustic streaming is responsible for the shift of stimulation threshold.