Neutrophil "priming" induced by orthovanadate: evidence of a role for tyrosine phosphorylation

The mechanism of neutrophil "priming" is unknown. In this study the level of tyrosine phosphorylation within intact neutrophils, using orthovanadate, have been manipulated. It has been demonstrated that this procedure both increased tyrosine phosphorylation of a number of protein substrates, including a prominent band at 74 kDa, and also primed the neutrophil oxidase response with a time and orthovanadate concentration-dependency, which were consistent with a role for tyrosine phosphorylation. No effect of orthovanadate on cytosolic-free Ca2+ concentration or actin polymerization was detected. Inhibition of tyrosine phosphorylation by genistein prevented "priming" by orthovanadate. This data thus provided evidence of a role for tyrosine phosphorylation in neutrophil "priming".