PROTEIN-KINASE-C ACTIVITY IS ALTERED IN HL60 CELLS EXPOSED TO 60 HZ AC ELECTRIC-FIELDS

We examined the effects of electric fields (EFs) on the activity and s ubcellular distribution of protein kinase C (PKC) of living HL60 cells . Sixty Hertz AC sinusoidal EFs (1.5-1,000 mV/cm p-p) were applied for 1 h to cells (10(7)/ml) in Teflon chambers at 37 degrees C in the pre sence or absence of 2 mu M phorbol 12-myristate 13-acetate (PMA). PMA stimulation alone evoked intracellular translocation of PKC from the c ytosolic to particulate fractions. Ln cells that were exposed to EFs ( 100-1,000 mV/cm) without PMA, a loss of PKC activity from the cytosol, but no concomitant rise in particulate PKC activity, was observed. In the presence of PMA, EFs (33-330 mV/cm) also accentuated the expected loss of PKC activity from the cytosol and augmented the rise in KC ac tivity in the particulate fraction. These data show that EFs alone or combined with PMA promote down-regulation of cytosolic PKC activity si milar to that evoked by mitogens and tumor promoters but that it does not elicit the concomitant rise in particulate activity seen with thos e agents. (C) 1996 Wiley-Liss, Inc.