Effects of adenosine on inositol 1,4,5-trisphosphate formation and intracellular calcium changes in formyl-Met-Leu-Phe-stimulated human neutrophils.

In the presence of adenosine, formyl-Met-Leu-Phe-stimulated human neutrophils show a greatly diminished production of superoxide anion. Analysis of changes in levels of intracellular calcium revealed that the immediate increase (occurring within seconds) in intracellular calcium following addition of formyl-Met-Leu-Phe is not affected by the presence of adenosine, although there are significantly lower intracellular calcium levels during the late phase (occurring 1-4 min after addition of formyl-Met-Leu-Phe). Consistent with these findings is the fact that adenosine does not affect the production of inositol 1,4,5-triphosphate in formyl-Met-Leu-Phe-stimulated neutrophils. These data suggest that the profound inhibitory effects of adenosine on superoxide responses in formyl-Met-Leu-Phe-stimulated neutrophils may be related to an action of adenosine occurring late in the sequence of events of signal transduction.