THE RELATIONSHIP OF SCATTERED SUBHARMONIC, 3.3-MHZ FUNDAMENTAL AND 2ND-HARMONIC SIGNALS TO DAMAGE OF MONOLAYER CELLS BY ULTRASONICALLY ACTIVATED ALBUNEX(R)

Cultured Chinese hamster ovary cells attached to thin Mylar sheets wer e exposed to 3.3-MHz ultrasound in the presence of Albunex(R) ultrasou nd contrast agent. The ultrasound beam was directed upward at the expo sure chamber with the monolayer on the inside of the upper acoustic wi ndow. Cell membrane damage was detected by the firefly enzyme assay fo r released ATP and the subharmonic, fundamental, and second harmonic s cattered signals were recorded. ATP release increased monotonically wi th increasing pressure amplitude above apparent thresholds of 0.28 MPa for 1-s continuous and 0.56 MPa for 100-s pulsed (10-mu s pulses, 1-m s PRP) exposures with 5% Albunex(R). The subharmonic signal and, to a lesser extent, the second harmonic signal both increased with the cell membrane damage, which suggests that these signals have predictive va lue for bioeffects. If the monolayer was positioned on the front windo w of the exposure chamber, cell membrane damage was greatly reduced, w hich confirms the protective influence of this configuration of monola yers reported in the literature. The effect decreased both at high (50 %) or low (0.5%) concentrations of Albunex(R). The strong nonlinear sc attering of ultrasound by contrast agent gas bodies appears to provide useful indicators of gas body activity including cavitational bioeffe cts. (C) 1998 Acoustical Society of America. [S0001-4966(98)06301-2].