Extracellular ATP stimulates poly(inositol phospholipid) hydrolysis and eicosanoid synthesis in mouse peritoneal macrophages in culture.

The effects of extracellular ATP on inositol phospholipid breakdown and synthesis of eicosanoids were studied in mouse peritoneal macrophages. Addition of ATP to intact cells labelled with [3H]inositol stimulated a rapid (within 10 s) formation of inositol 1,4,5-trisphosphate and inositol 1,3,4,5-tetrakisphosphate. In parallel there was also a substantial accumulation of inositol 1,3,4-trisphosphate and the monophosphate and bisphosphate derivatives of inositol. Within 10 s after the addition of 30 microM ATP there was a twofold increase in inositol trisphosphate (InsP3), which declined over 2 min. The ED50 for ATP-stimulated generation of InsP3 was approximately 12 microM. ADP and GTP showed only weak effects on InsP3 formation, while AMP and adenosine were completely ineffective at 30 microM. Furthermore, the rank order of potency of ATP analogues was ATP greater than ATP[S] greater than AdoPP[NH]P = AdoPP[CH2]P greater than AdoP[CH2]PP thus, indicating the presence of a P2y-purinergic receptor. Cells labelled with [3H]arachidonic acid showed a 50% increase of label in 1,2-diacylglycerol after 15 s upon stimulation with ATP. In parallel to the stimulation of inositol phospholipid hydrolysis, ATP also caused a marked synthesis of prostaglandin E2 (PGE2) and leukotriene C4 (LTC4) in mouse peritoneal macrophages. The rank order of potency of ATP analogues was identical with that of InsP3 generation. The effect on eicosanoid synthesis could be mimicked by the calcium ionophore A23187 and the phorbol ester 12-O-tetradecanoylphorbol 13-acetate. These results suggest that ATP-induced activation of P2y-purinergic receptors in mouse peritoneal macrophages triggers inositol phospholipid breakdown and eicosanoid synthesis.