Résumé : HL-60 cells are human promyelocytic cells expressing two ATP receptors: the P2Y(2) and P2Y(11) subtypes. Our Northern blotting experiments have shown that P2Y(2) and P2Y(11) messengers were up-regulated in these cells, rapidly and independently of protein synthesis, following treatment with granulocytic differentiating agents such as retinoic acid, dimethylsulfoxide, granulocyte-colony stimulating factor, dibutyryl cyclic AMP and ATP. AR-C67085 and adenosine 5'-O-(3-thiotriphosphate), two potent agonists of the recombinant P2Y(11) receptor, increased intracellular cAMP concentration in HL-60 cells more potently than ATP itself. These observations support the conclusion that the effect of ATP on HL-60 cell differentiation is mediated by the P2Y(11) receptor.