Rat uterine stromal cells (U I I I ) express pancreatic type PLA 2 (PLA 2 -I) receptor and internalize the enzyme bound to receptors. Here, we investigate the proliferating effect and alterations in binding of PLA 2 -I. There is a dramatic decline in PLA 2 -I binding in U I I I cells as they progress from a nonconfluent proliferating state (40,000 sites/cell) to a confluent state (1300 sites/cell). Intracellular concentration of PLA 2 -I changed with the alteration in binding, suggesting that regulation in the PLA 2 binding capacity may have important implications in growth control mechanisms.