• 1
    The amphotericin B-perforated whole-cell patch clamp technique was used to determine the modulation of L-type Ca2+ channels by protein kinase C (PKC)-mediated pathways in adult rat ventricular myocytes.
  • 2
    Application of 10 nM endothelin-1 (ET-1) increased peak Ca2+ current (ICa) by 28.2 ± 2.5 % (n= 13) and slowed current decay. These effects were prevented by the endothelin receptor antagonist PD145065 (10 μM) and by the PKC inhibitor chelerythrine (8 μM).
  • 3
    To establish if direct activation of PKC mimicked the ET-1 effect, the active and inactive phorbol esters (phorbol-12-myristate-13-acetate and 4α-phorbol-12, 13-didecanoate) were tested. Both phorbol esters (100 nM) resulted in a small (∼10 %) increase in ICa, suggesting PKC-independent effects.
  • 4
    Bath application of dioctanoylglycerol (diC8), a diacylglycerol (DAG) analogue which is capable of directly activating PKC, caused a gradual decline in peak ICa (50.4 ± 6.2 %, n= 5) and increased the rate of current decay. These effects were unaffected by the PKC inhibitor chelerythrine (8 μM).
  • 5
    Intracellular photorelease of caged diC8 with 3 or 10 s exposure to UV light produced a concentration-dependent increase in peak ICa (20.7 ± 8.5 % (n= 8) for 3 s UV and 60.8 ± 11.4 % (n= 13) for 10 s UV), which could be inhibited by chelerythrine.
  • 6
    Our results demonstrate that both ET-1 and intracellularly photoreleased diC8 increase ICa by a PKC-mediated pathway, which is in direct contrast to the PKC-independent inhibition of ICa produced by bath-applied diC8. We conclude that specific cellular pools of DAG are crucially important in the regulation of ICa by PKC.