Participation of phospholipase A(2) isoforms in the control of calcium influx into electrically non-excitable cells

The participation of phospholipase A(2) isoforms in capacitative store-oper ated Ca2+ influx into Jurkat leukemic T and MDCK cells was investigated. Pr eincubation of Jurkat cells with either bromophenacyl bromide (an inhibitor of secreted phospholipase A(2), sPLA(2)) or Helss (an inhibitor of calcium independent phospholipase A(2) - iPLA(2)) resulted in a significant inhibi tion of the calcium influx. The extent of this inhibition depended on the p H of the extracellular millieu; it increased with alkalisation. The rate of Ca2+ influx into MDCK cells was reduced by bromophenacyl bromide. Preincub ation of these cells with Helss resulted in the stimulation of the influx. These observations suggest the participation of different PLA(2) isoforms i n the regulation of Ca2+ influx. They also show that the extent that PLA(2) isoforms control the influx depends on the pH of the medium. Finally, thes e data indicate that various phospholipase A(2) isoforms may play a role in the control of Ca2+ influx in different cell lines.