BIOCHEMICAL AND MORPHOLOGIC EFFECTS OF CAVITATION ON NORMAL HUMAN PLATELETS
FREED, DEBOW, II
Doctor of Philosophy
The objective of this study was to investigate the physical and biochemical response of platelets subjected to well-defined vaporous cavitation near a decelerating prosthetic surface. Also examined was the hypothesis that two types of shear stress transients, lytic and sublytic, are responsible for platelet lysis, aggregation and functional impairment which has been observed in previous studies of acoustic cavitation. Platelet-rich plasma was exposed to 1000 cycles of low-intensity cavitation in a specially modified apparatus at 23(DEGREES)C for approximately 30 minutes. To determine which of the three known pathways of platelet aggregation might be involved, a small study using 50 (mu)M aspirin was conducted. Particle size data obtained with the Coulter counter indicate that cavitation causes both lysis and aggregation. Biochemical assays indicate that release of granular contents occurs, and that platelet functional capacity is irreversibly damaged after exposure to cavitation. Results of the drug study indicate that aspirin pretreatment of platelets (which inhibits the thromboxane pathway) almost completely abolishes cavitation-induced aggregation and impaired functional capacity. The data from this study are consistent with the dual effect of cavitation postulated by Dube: those platelets sufficiently close to a collapse event are lysed by shear transients, while those somewhat farther away are stimulated to aggregate in response to sublytic shear stresses or to soluble factors leaked from mechanically disrupted platelets and their fragments. The clinical implications of this study are manifold.