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 [Ca(2+)] 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 Ca(2+). Calcium imaging of the cells was performed using digital video fluorescence microscopy and Ca(2+)-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 Ca(2+). These cells exhibited a large influx of Ca(2+) over 3-4 s and did not return to their equilibrium levels. Subsequently, some cells exhibited one or more Ca(2+) 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.
Kumon
R E
RE
Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA.
Aehle
M
M
Sabens
D
D
Parikh
P
P
Kourennyi
D
D
Deng
C X
CX
D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D016466:CHO Cells; D020013:Calcium Signaling / Q000502:physiology*; D006224:Cricetinae; D003412:Cricetulus; D045423:Microbubbles / Q000009:adverse effects; D008856:Microscopy, Fluorescence; D018715:Microscopy, Video; D013314:Stress, Mechanical; D014465:Ultrasonics / Q000009:adverse effects