['This study was undertaken to determine the effect of the topical application of diadenosine tetraphosphate on lactoferrin levels in rabbit tears.', 'Diadenosine tetraphosphate was topically instilled in a single-dose, tear samples were collected by micropipette and lactoferrin was measured by Enzyme-Linked ImmunoSorbent Assay (ELISA).', 'The concentration of lactoferrin in rabbit tears was significantly increased 1 h after diadenosine tetraphosphate application, remaining elevated for 3 h more. This effect was blocked by P2 receptors antagonists.'] Are lactoferrin Levels in Tears Increased by the Topical Application of Diadenosine Tetraphosphate?