Interleukin-1 (IL-2) stimulated the release of PGE2 in Swiss 3T3 cells. Pretreatment of the cells with IL-2 enhanced the bradykinin stimulated release of PGE2 10 fold. Similar enhancement was seen for bombesin and thrombin IL-2 induced phospholipase A2 cyclooxygenase, and GTPase but did not alter receptor number of affinity. Diacyglycerol also stimulated phospholipase A2 activity in the Swill 3T3 cells. Unique bradykinin receptors unlike the previously described B1 and B2 classification were pharmacologically identified using several bradykinin analogs. These receptors were further characterized according to their differential coupling to phospholipase-C and phospholipase A2 signal transduction systems. Muscarinic receptors m1, m3 and m5 transfected into fibroblasts stimulated arachidonic acid release, inositolphospholipid turnover and cAMP accumulation. Muscarinic receptors m2 and m4 caused a decrease in cAMP accumulation. The receptor mediated release of arachidonic acid was distinct from inositolphospholipid turnover. PMA and carbachol caused a carbachol caused a synergistic stimulation of arachidonic acid release, but PMA inhibited inositolphospholipid turnover. Dopamine-1 receptors stimulated inositolphospholipid turnover in renal cortical plasma membranes. This stimulation was independent of adenylate cyclase activity and appear to be linked to phospholipase-C via a cholera and pertussin toxin insensitive guanine nucleotide binding protein. A Specific GTP-binding protein, transducin, has been demonstrated to function in the receptor-mediated activation of phospholipase A2 and C in bovine retina. Both phospholipases appear to be under inhibitory control in this tissue. Kinases appear to play a role in the signal transduction of phospholipase A2 and phospholipase C by modification of the G proteins that couple receptor activation to changes in effector systems within the cell.
