Comparative sensitivity of human and bovine erythrocytes to sonolysis by 1-MHz ultrasound

This project tested the hypothesis that human erythrocytes, being larger th an bovine erythrocytes, would be the more sensitive to sonolysis induced by inertial cavitation. The rationale behind this hypothesis was an earlier d emonstration that, among sized populations of erythrocytes, an inverse rela tion existed between erythrocyte volume and mechanically-induced shear forc es in the surrounding medium; viz, the larger the cell, the less shear forc e required to rupture the cell's membrane. At low erythrocyte densities (i. e., approximately 5% hematocrit) the hypothesis was supported; at high cell densities (i.e., approximately 35% hematocrit) it was not supported. The d ata are consistent with an ultrasound (US)-induced symmetric implosion of a ffected gas nuclei as causing the effect at low cell densities; under such conditions there is ample spacing among cells for US-induced symmetric grow th and collapse of gas nuclei and the concomitant production of radially-ex panding shock waves (which lyse the cells); at high cell densities there is not sufficient spacing among cells for US-induced symmetric growth and col lapse of bubbles and an alternative mechanism, possibly asymmetric bubble c ollapse, becomes operational. (C) 2000 World Federation for Ultrasound in M edicine & Biology.