Nitric oxide synthesis mediated by uracil nucleotides in lipopolysaccharide (LPS) cultures. Cells were incubated with UDP or PSB 0474 for 48 h. The P2Y6 antagonist MRS 2578 and enzyme inhibitors were added to the medium 1 h before the nucleotides. The concentration of nitrites plus nitrates was evaluated in the culture supernatants and was expressed as percentage of change from the respective control. Values are means ± SEM from four experiments. *P <0.05, significant differences from the respective control; +P <0.05, significant differences from the agonist alone.