MASTOPARAN EVOKES EXOCYTOSIS WITHOUT CA2+ MOVEMENT IN ADRENAL CHROMAFFIN CELLS

The secretagogue action of mastoparan, a tetradecapeptide from wasp ve nom, was studied in adrenal chromaffin cells. Pulsatile stimulation wi th mastoparan evoked a sharp transient release of CA in a dose-depende nt manner, as measured by real-time monitoring system. The secretagogu e action of mastoparan in these cells was apparently independent of ex tracellular Ca2+, and may not require the intracellular mobilization o f Ca2+ since BAPTA failed to block its secretagogue action. Video-imag ing data also suggested that mastoparan evokes CA release without an i ncrease in the intracellular Ca2+. In addition, visualization of exocy totic events with video-enhanced light microscopy demonstrated that CA release evoked by mastoparan at relatively low concentration was inde ed mediated by exocytotic process, not by cell lysis.