Direct demonstration of increased intracellular concentration of free calcium in rabbit and human neutrophils following stimulation by chemotactic factor

Abstract An increase in the level of intracellular free calcium concentration in rabbit and human neutrophils stimulated by chemotactic factors has been demon-strated directly using the calcium-sensitive fluorescent probe quin-2. Addition of f-Met-Leu-Phe (10 −9 M), C5 a (3×10 −9 M) or leukotriene B 4 (6 × 10 −8 M) to the neutrophils induces a rapid increase in the intracellular concentration of free calcium that reaches a maximum value 15 seconds following stimulation. At concentrations of f-Met-Leu-Phe less than 10 −8 M the enhancement is dose dependent with an ED 50 of 8 × 10 −11 M and is significantly reduced in the presence of EGTA in the suspending medium.