Effects of phorbol ester on intracellular Ca2+ and membrane currents in cultured human microglia.
The effects of protein kinase C (PKC) activation by phorbol ester on intracellular Ca2+ concentration ([Ca2+]i) and membrane currents in human microglia grown in culture were investigated. Treatment of microglia with phorbol myristate acetate (PMA) resulted in a large increase in [Ca2+]i in cells loaded with fura-2. The increased levels of [Ca2+]i were not altered following removal of the phorbol ester. In Ca(2+)-free medium, application of PMA did not increase [Ca2+]i. In addition, PMA application in standard Ca(2+)-solution containing lanthanum (1.8 mM) had no effect on the microglial response to PMA, suggesting that the phorbol ester actions were due to transmembrane influx of Ca2+ but not through voltage-gated Ca2+ channels. Whole-cell patch clamp measurements demonstrated that PMA potentiated an outward K+ current and inhibited an inward rectifier K+ current. This study is the first demonstration that PKC activation by phorbol ester leads to increased intracellular [Ca2+] and changes in membrane currents in human microglia.
Yoo
A S
AS
Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, Canada.
McLarnon
J G
JG
Xu
R L
RL
Lee
Y B
YB
Krieger
C
C
Kim
S U
SU
D001921:Brain / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured / Q000187:drug effects; D005333:Fetus / Q000187:drug effects; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects*; D017628:Microglia / Q000187:drug effects* / Q000378:metabolism; D010703:Phorbol Esters / Q000494:pharmacology*
D010703:Phorbol Esters; D002118:Calcium