Influence of tilapia mast cell lysate on vascular permeability.

Kinetics of vascular permeability was determined by measuring the amount of Evans blue leaked into the tilapia mast cell (tMC)-lysate injection site. Injection with tMC lysate enhanced the vascular permeability. The response consisted of three distinct phases, the first started immediately after the injection, the second started at about 2 h, reaching its maximum at 4 h, and the third response started at 12 h and continued for more than 24 h. Heating of the tMC lysate at 100 degrees C for 10 min had no effect on the first response, while the second response was significantly reduced by heating at 50 degrees C for 10 min. The tMCs seem to have two kinds of factors that enhance vascular permeability. The tMC lysate induced Ca2+ uptake by cultured tilapia endothelial cells, indicating that tMC products directly activate the endothelial cells and increase vascular permeability similar to products of mammalian mast cells. These results indicate that with respect to influence on vascular permeability tilapia mast cells resemble the mast cells of mammals.