Ultrasound-Induced Calcium Oscillations and Waves in Chinese Hamster Ovary Cells in the Presence of Microbubbles

This study investigated the effects of ultrasound on the intracellular [Ca2+] of Chinese hamster ovary cells in the presence of albumin-encapsulated Optison microbubbles. Cells were exposed to 1 MHz ultrasound (tone burst of 0.2 s duration, 0.45 MPa peak pressure) while immersed in solution of 0.9 mM Ca2+. Calcium imaging of the cells was performed using digital video fluorescence microscopy and Ca2+-indicator dye fura-2AM. Experimental evidence indicated that ultrasound caused a direct microbubble-cell interaction resulting in the breaking and eventual dissolution of the microbubble and concomitant permeabilization of the cells to Ca2+. These cells exhibited a large influx of Ca2+ over 3–4 s and did not return to their equilibrium levels. Subsequently, some cells exhibited one or more Ca2+ oscillations with the onset of oscillations delayed by 10–80 s after the ultrasound pulse. A variety of oscillations were observed including decaying oscillations returning to the baseline value over 35– 100 s, oscillations superimposed on a more gradual recovery over 150–200 s, and oscillations continued with increased amplitude caused by a second ultrasound tone burst. The delays in onset appeared to result from calcium waves that propagated across the cells after the application of the ultrasound pulse.NIH grant R01CA116592American Cancer Society Institutional Research Grant to Case Western Reserve UniversityPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/84354/1/L29.pd