Uridine-5-diphosphate disodium salt (UDP disodium salt) is a specific agonist of the P2Y6 receptors (EC50 = 13 nM for human P2Y6), stimulating the production of inflammatory mediators, phagocytosis, and vasoconstriction. Uridine-5-diphosphate disodium salt also acts as an antagonist of P2Y14.