Lenka Forýtková

Effect of ultrasound on DNA synthesis in tumor cells

The objective of this study was to consider the influence of continuous-wave (CW) ultrasound (800 kHz) on DNA synthesis in Ehrlich ascitic tumor cells in vitro. The 10-min irradiation was carried out in rotating polyethylene tubes (5 rpm). Incorporation of 3H-thymidine was employed to detect DNA synthesis. Replication and unscheduled (repair) DNA synthesis were distinguished by means of hydroxyurea treatment before insonation. It was established that the use of 0.5 W/cm2 and 1.0 W/cm2 (ISA) CW ultrasound interfered with DNA synthesis showing up as inhibition. The inhibition became most noticeable when starting insonation in a sample cooled to 5 degrees C. During insonation, the sample temperature was allowed to increase to the ambient (water bath) temperature of 37 degrees C. However, at an ultrasound intensity (SA) of 0.1 W/cm2 such inhibition was not proven, but a moderate stimulation of DNA synthesis was demonstrated. Changes in DNA synthesis after insonation were found to be transient because of a lack of stimulatory and/or inhibitory ultrasound effects after 1-h incubation at 37 degrees C. In our experimental conditions no effects on DNA synthesis due to the effects of the insonated medium on the cells were discernible. No statistically significant changes in unscheduled DNA synthesis were observed. Possible action mechanisms are discussed.