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Apocynin inhibits and its removal augments L‐type Ca2+ currents in coronary artery smooth muscle cells and ventricular myocytes
Author(s) -
Ochi Rikuo,
Gupte Rakhee S,
Murayama Takashi,
Kurebayashi Nagomi,
Gupte Sachin A
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.595.7
Subject(s) - apocynin , nadph oxidase , reactive oxygen species , chemistry , myocyte , oxidase test , superoxide , medicine , biophysics , microbiology and biotechnology , biochemistry , endocrinology , biology , enzyme
Exogenously applied H 2 O 2 augments L‐type Ca 2+ current ( I Ca,L ). NADPH oxidase (NOX) initiates sequential reactions to generate reactive oxygen species (ROS) including H 2 O 2 . We studied the regulatory role of NOX‐generated ROS on I Ca,L by applying apocynin (APO), a NOX inhibitor, and diphenyleneiodonium (DPI), a flavoprotein inhibitor. Whole cell I Ca,L was recorded from bovine coronary arterial smooth muscle (BCASMC), rat ventricular myocytes (RVMC) and HEK 293 cells transiently expressing human cardiac Ca V 1.2. APO (0.1–10 mM) rapidly and dose‐dependently inhibited I Ca,L : 10‐mM APO decreased I Ca,L to 27, 34 and 16% in BCASMC, RVMC and 293 cells, respectively, while DPI (10 μM) inhibited more slowly and less intensively (to 64% in RVMC). The inhibitory effects of both inhibitors were mainly additive. Surprisingly, washout of high concentrations of APO rapidly recovered I Ca,L to slightly above control in BCASMC and increased to 150% of control with prolonged current decay in RVMC. ROS levels measured simultaneously with I Ca,L by increase rate of CM‐H 2 DCF fluorescence were decreased by APO and markedly increased by its removal in BCAVSM and RVMC. Possible accumulation of NADPH during NOX inhibition by APO explains the increased generation of ROS. We conclude that decrease of ROS inhibits and its increase augments cardiovascular I Ca,L and NOX is involved in the regulation of I Ca,L . This study is supported by NIH grant #R01HL85352