Regulation of superoxide responses of human neutrophils by adenine compounds. Independence of requirement for cytoplasmic granules

Recent evidence suggests that the adenine compounds ATP, adenosine-5'-O-(3-thiotriphosphate) (ATP gamma S), and adenosine have important regulatory effects on O2- responses of human neutrophils stimulated with the chemotactic peptide N-formyl-Met-Leu-Phe (fMLP). Because of evidence that receptors on neutrophils may be modified by granule fusion events, we assessed the extent to which these adenine compounds affect fMLP and CR3 (C3bi) receptors on neutrophils and whether cytoplasmic granules are required for the ability of the adenine compounds to modify O2- responses in neutrophils stimulated with fMLP. Incubation of neutrophils with ATP gamma S or adenosine led to a decrease in numbers of fMLP receptors (17 and 9.2%, respectively) but no change in receptor affinity (Kd). Paradoxically, ATP gamma S caused an increase in CR3 receptors (Mo1, CD-11b antigen), suggesting that fMLP and CR3 receptors may be under separate control. The ability of the adenine compounds to modify O2- responses in fMLP-stimulated cells was equivalent in both neutrophils and cytoplasts, suggesting that the regulatory effect of ATP, ATP gamma S, and adenosine do not require the presence of cytoplasmic granules. ATP gamma S caused enhancement of O2- responses of neutrophils to phorbol 12-myristate 13-acetate, raising the possibility that ATP gamma S may be affecting late events in the signal transduction pathway.