A comparative study of arachidonic acid metabolism in rabbit cultured astrocytes and human astrocytoma cells (1321N1)

1. 1. ATP, bradykinin (BK), and A-23187 activated the generation of prostaglandin (PG) E 2 and thromboxane (TX) B 2 in rabbit astrocytes, but not in human astrocytoma cells (1321N1). 2. 2. In human astrocytoma cells, ATP, BK, and A-23187 could not release [ 3H]arachidonic acid (AA) from [ 3H]AA-labeled cells and exogenous AA was not converted to TXB 2 and PGE 2, suggesting the lack of phospholipase (PL) A 2 and cyclooxygenase activities in 1321N 1 human astrocytoma cells, although they express TXA 2 receptors. 3. 3. In rabbit astrocytes, ATP and BK, but not A-23187, showed increased accumulation of inositol phosphates, indicating that an increase in intracellular Ca 2+ concentration alone would not be enough to activate PLC. Furthermore, indomethacin, a cyclooxygenase inhibitor, partially attenuated ATP-induced phosphoinositide hydrolysis, indicating that cyclooxygenase product(s) would secondarily activate PLC in response to ATP.