Antimicrobial beta-defensins are thought to protect epithelial surfaces. Their mobilization in response to inflammation was studied in the rat parotid gland using an ELISA assay. Bacterial lipopolysaccharide (LPS), injected into the parotid duct on one side, induced a marked local inflammatory response in the parotid gland as judged by several fold increases in myeloperoxidase activity and, in histological sections, infiltration of neutrophils. Three hours after the injection, beta-defensin 1 and 3 were increased (by 41% and 15%, respectively, P<0.01) as compared to the contralateral gland. Though still elevated 6h after the injection, the percentage figures for beta-defensin 1 were, at this time, somewhat lower (30%) compared to the situation at 3h, while those for defensin 3 were significantly higher 65% (P<0.01); neither at the early nor at the late time of observation were any changes in the level of beta-defensin 2 observed. The beta-defensins under study were not detected in submandibular and sublingual glands, neither were they detected in the inflamed submandibular gland, showing also here several fold increases in myeloperoxidase activity and, in addition, the presence of inflammatory cells, following ductal injection of LPS towards the gland.