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Endothelin‐1 and photoreleased diacylglycerol increase L‐type Ca 2+ current by activation of protein kinase C in rat ventricular myocytes
Author(s) -
He JiaQiang,
Pi YeQing,
Walker Jeffery W.,
Kamp Timothy J.
Publication year - 2000
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2000.00807.x
Subject(s) - chelerythrine , protein kinase c , diacylglycerol kinase , phorbol , endothelin 1 , biophysics , chemistry , tetradecanoylphorbol acetate , medicine , intracellular , endocrinology , biochemistry , biology , kinase , receptor
1 The amphotericin B‐perforated whole‐cell patch clamp technique was used to determine the modulation of L‐type Ca 2+ channels by protein kinase C (PKC)‐mediated pathways in adult rat ventricular myocytes. 2 Application of 10 nM endothelin‐1 (ET‐1) increased peak Ca 2+ current ( I Ca ) 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 I Ca , suggesting PKC‐independent effects. 4 Bath application of dioctanoylglycerol (diC 8 ), a diacylglycerol (DAG) analogue which is capable of directly activating PKC, caused a gradual decline in peak I Ca (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 diC 8 with 3 or 10 s exposure to UV light produced a concentration‐dependent increase in peak I Ca (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 diC 8 increase I Ca by a PKC‐mediated pathway, which is in direct contrast to the PKC‐independent inhibition of I Ca produced by bath‐applied diC 8 . We conclude that specific cellular pools of DAG are crucially important in the regulation of I Ca by PKC.