THE AUGMENTATION OF LEUKOCYTE ADHESION TO ENDOTHELIUM BY THERAPEUTIC ULTRASOUND

To determine the effects of exposure of endothelial cells to therapeut ic ultrasound on leucocyte adhesion to these cells, confluent cultures of bovine aortic endothelial cells in tissue culture flasks and on co llagen coated coverslips were exposed to a maximum of 1.6 W/cm2 1 MH(z ) continuous ultrasound for 15 min, then incubated with neutrophil-ric h suspensions containing a known number of viable human leucocytes for intervals from 1 to 240 min. After incubation, nonadherent cells were decanted, the number of leucocytes in the eluted suspension determine d and the percentage of adhered cells calculated. Endothelial cell via bility was not significantly reduced by ultrasound or by incubation wi th leucocytes. Whereas untreated endothelial cells were flattened and had surface microvilli, those exposed to ultrasound were plump, rounde d and more widely separated along their borders. The percentage of leu cocytes that adhered to sonicated endothelium was significantly higher , and this proportion increased with the duration of incubation. Thus, exposure of endothelial cells to ultrasound in vitro can cause interc ellular separation and increase the adhesion to leucocytes. If such ch anges were also to occur in vivo, therapeutic ultrasound would potenti ate the inflammatory response.