Interactions of leukocytes with endothelium play a role for the immune system modulated by endogenous agents, such as glucocorticoids and nitric oxide (NO). Glucocorticoids inhibit leukocyte-endothelial interactions whereas the role of NO is still controversial. In this study, the activity of Ca(+2)-dependent nitric oxide synthases was in vivo blocked in male Wistar rats by given l-NAME, 20mgkg(-1) for 14 days dissolved in drinking water and expression of adhesion molecules involved in leukocyte-endothelial interactions was investigated. Expressions of L-selectin and PECAM-1 in peripheral leukocytes and PECAM-1 in endothelial cells were reduced by l-NAME treatment. Only L-selectin expression was controlled at transcriptional levels. These effects were not dependent on endogenous glucocorticoids, as corticosterone levels were not altered in l-NAME-treated rats. Our results show that NO, produced at physiological levels, controls expression of constitutive adhesion molecules expressions in cell membranes by different mechanisms of action.