Bovine culture endothelial cells (BAECs) generate platelet-activating factor (Paf) following activation by bradykinin (Bk 0.1 nM), the ionophore, A23187 (3 microM), and ATP (10 microM), but Paf is not released from the cells. These stimuli also elicit generation of prostacyclin (PGI2). The specific and competitive Paf receptor antagonists, WEB 2086 (0.1-1.0 microM) and CV 6209 (0.01-0.1 microM), inhibited Bk-, A23187- and, to a lesser extent, ATP-induced PGI2 generation but had no effect on basal PGI2 generation. These data suggest a role for intracellular Paf in signal transduction.