Aspects of the haemolytic reaction induced by Kanagawa haemolysin of Vibrio parahaemolyticus.

Vibrio parahaemolyticus, an important enteric pathogen, produces toxin (Kanagawa haemolysin, KH), the presence of which correlates well with pathogenicity. KH induced lysis of human red blood cells (HRBC); the kinetics were strongly dependent on KH concentration (0-1 HU/ml) and rather independent of target cell concentration [0.5 < or = haematocrit (%) < or = 6] and the ratio KH:HRBC. The suggestion that KH-induced haemolysis is due to colloid osmosis is supported by results indicating: (1) osmotic protection (by suspension in iso-osmotic choline chloride, D-sorbitol or L-valine, or MOPS-buffered saline with added sucrose), (2) a cell volume increase prior to lysis, and (3) an increase in HRBC cation (86Rb+) influx after KH addition, indicating raised passive cation permeation. The effect of temperature on KH-induced haemolysis indicates the importance of processes other than the action of a simple water-filled pore, because of the high activation energy [53.30 +/- 2.79 kJ (mol.)-1] involved. Although haemolytic rate was attenuated by washout after 5 min KH exposure, the KH-induced lesion itself was not susceptible to washout by either extracellular volume expansion (at constant osmolarity) or centrifugation/resuspension. This suggests that HRBC binding of KH from aqueous solution still continues after 5 min exposure at 37 degrees C. Pre-vortexing KH with dibutyl phthalate (DBP) dramatically reduced the haemolytic activity of the aqueous toxin preparation, suggesting a protein-lipid interaction, which may support the contention that KH can move from a hydrophilic to a hydrophobic environment. Two features were identified that are characteristic of highly purified TDH preparations: (1) thermostability of haemolysin, and (2) monovalent cation selectivity series of lesion: Cs+ > Li+ > K+ > Rb+ > Na+, confirming that TDH is the important leak-inducing agent of KH.