Chemokines are small, secreted proteins (5-15 kDa) that mediate leukocyte transmigration and can be secreted from endothelial cells in a constitutive or regulated manner. Regulated secretion shortens the response time to inflammatory stimuli because the chemokine is produced in advance and not dependent on de novo synthesis. The existence of regulated chemokine secretion from endothelial cells hasnot yet been demonstrated in animal models. A homologue of the potent neutrophilattracting chemokine IL-8 has not been found in rodents. However, other potent neutrophil chemoattractants such as CXCL1,CXCL2, and CXCL6 were therefore analyzed by immunohistochemistry in experimental acute peritonitis/sepsis and in DSS-induced colitis, with special emphasis on their possible sorting to Weibel-Palade bodies (WPB). The data presented imply that sorting to WPB for regulatedchemokine secretion is not a prominent feature of rodent endothelial cells but also indicate that MIP-2 may be sorted to another granular compartment in resting mesenteric vessels, perhaps related to the type II compartment of regulated secretion recently described in human endothelial cell cultures.