A COMPARATIVE-STUDY OF ARACHIDONIC-ACID METABOLISM IN RABBIT CULTUREDASTROCYTES AND HUMAN ASTROCYTOMA-CELLS (1321N1)

1. ATP, bradykinin (BK), and A-23187 activated the generation of prost aglandin (PG) E(2) and thromboxane (TX) B-2 in rabbit astrocytes, but not in human astrocytoma cells (1321N1). 2. In human astrocytoma cells , ATP, BK, and A-23187 could not release [H-3]arachidonic acid (AA) fr om [H-3]AA-labeled cells and exogenous AA was not converted to TXB(2) and PGE(2), suggesting the lack of phospholipase (PL) A(2) and cycloox ygenase activities in 1321N1 human astrocytoma cells, although they ex press TXA(2) receptors. 3. In rabbit astrocytes, ATP and BK, but not A -23187, showed increased accumulation of inositol phosphates, indicati ng that an increase in intracellular Ca2+ concentration alone would no t be enough to activate PLC. Furthermore, indomethacin, a cyclooxygena se inhibitor, partially attenuated ATP-induced phosphoinositide hydrol ysis, indicating that cyclooxygenase product(s) would secondarily acti vate PLC in response to ATP.