Cytokines play an important role in modulating cellular function. The effect of tumor necrosis factor alpha (TNF-alpha) on the metabolism of proteoglycans (PGs) was studied in mouse aortic endothelial cells (MAE). Confluent and exponentially growing cells were labeled with [35S] sulfate and [3H] glycine, and PGs isolated from the secreted, the pericellular, and intracellular pools. TNF-alpha influenced the metabolism of MAE PGs. This effect of TNF-alpha was dependent on the growth state of the cells. Nondividing MAE secrete PGs that have higher net negative charge than PGs from exponentially growing cells. TNF-alpha treatment further increased the net negative charge of PGs secreted from nondividing cells. Treatment of MAE with TNF-alpha caused a substantial decrease in the sulfation of PGs isolated from pericellular pool of nondividing cells, while it had the opposite effect on pericellular PGs isolated from dividing cells. Our results indicate that changes in PGs metabolism induced by TNF-alpha may contribute to the disturbance of vascular endothelial homeostasis associated with vascular injury in a variety of disease states.