Premium
L‐type Ca2+ channel current from on‐cell patch is augmented by H2O2 in rat aortic smooth muscle–derived A7r5 cells
Author(s) -
Ochi Rikuo,
Gupte Sachin A
Publication year - 2012
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.26.1_supplement.695.4
Subject(s) - extracellular , depolarization , patch clamp , intracellular , biophysics , chemistry , voltage dependent calcium channel , membrane potential , calcium , l type calcium channel , smooth muscle , aorta , anatomy , electrophysiology , medicine , endocrinology , biology , biochemistry , organic chemistry
L‐type Ca 2+ channels are exposed to H 2 O 2 generated within the cells and adjacent cells such as immune cells. Although the effect of H 2 O 2 on I Ca,L has long been studied, whether it augments or inhibits I Ca,L has not yet been settled. We hypothesized that extracellular and intracellular H 2 O 2 differently modulates I Ca,L . Here, we adopted two configurations of patch clamp technique to separately study these modulations in A7r5 cells, a smooth muscle cell line derived from embryonic rat aorta. Whole cell I Ca,L recorded with 10 mM Ba 2+ as a charge carrier was slightly inhibited with an acceleration of its decay time course by 0.1‐mM H 2 O 2 . On‐cell recording enabled us to study the effect of H 2 O 2 without possible complication of direct oxidation of Ca V 1.2 by external H 2 O 2 . Single and multichannel I Ca,L were recorded in the presence of 90 mM Ba 2+ and Bay K 8644 repetitively applying 500 ms depolarization steps to ‐10 and 0 mV. The mean currents from these currents were significantly increased by 0.1‐mM H 2 O 2 from 0.85 pA to 1.05 pA associated with slow inactivation: I Ca,L at 500 ms, 0.56 pA in control and 0.74 pA in the presence of H 2 O 2 . Since extracellular H 2 O 2 was not accessible to the patch membrane, these changes reflect intracellular actions of H 2 O 2 . In conclusion, I Ca,L is augmented by H 2 O 2 via intracellular signaling mechanism in A7r5 cells. Supported by National Heart, Lung, and Blood Institute Grant RO1‐HL‐085352.