Interleukin-1β induces gene expression and secretion of the secretory phospholipase A 2 (sPLA 2 ) and prostaglandin E 2 (PGE 2 ) release from rat mesangial cells. We have previousy shown that prolonged treatment of rat mesangial cells with interleukin-1β (IL-1β) also enhances the cytosolic phospholipase A; (cPLA 2 ) activity. This effect of IL-1β on the cPLA 2 activity is inhibited by actinomycin D and cycloheximide, indicating that both transcription and translation are involved. Here, we describe that IL-1β increases mRNA levels and protein synthesis of cPLA 2 itself. In parallel with the effect of dexamethasone on the sPLA 2 , this glucocorticoid inhibits the IL-1β-enhanced cPLA 2 activity as a result of the suppression of IL-1β-induced cPLA 2 gene expression. This report suggests that the pro-inflammatory action of interleukin-1β may, in part, be mediated by its effects on cPLA 2 activity.