Single cGMP-activated Ca2+-dependent Cl- channels in rat mesenteric artery smooth muscle cells
The present study describes the single channel properties of a novel cGMP-activated Ca 2+ -dependent Cl â channel in rat mesenteric artery smooth muscle cells. Single channel currents were recorded in cell-attached patches in the presence of 8Br cGMP in response to the addition of caffeine or nora...
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Published in | The Journal of physiology Vol. 555; no. 2; pp. 397 - 408 |
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Main Authors | , |
Format | Journal Article |
Language | English |
Published |
9600 Garsington Road , Oxford , OX4 2DQ , UK
The Physiological Society
01.03.2004
Blackwell Publishing Ltd Blackwell Science Inc |
Subjects | |
Online Access | Get full text |
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Summary: | The present study describes the single channel properties of a novel cGMP-activated Ca 2+ -dependent Cl â channel in rat mesenteric artery smooth muscle cells. Single channel currents were recorded in cell-attached patches in the
presence of 8Br cGMP in response to the addition of caffeine or noradrenaline and in both outside-out and inside-out patches
when the internal patch surface was bathed in cGMP and Ca 2+ . The channels were permeable to Cl â ions with an anion permeability sequence of SCN â (1.7) > Cl â (1.0) > I â (0.6). Single channel mean open probability ( NP o ) was independent of voltage and the channels displayed three conductance levels of 15, 35 and 55 pS. cGMP was required for
channel activation and the single channel NP o increased sharply with raised [Ca 2+ ] i , maximal activation occurring at a [Ca 2+ ] i of about 100 n m . The relationship between NP o and cGMP concentration was voltage independent and could be fitted by the Hill equation giving a K d of about 3 μ m and a Hill coefficient ( n H ) of 3. cGMP- and Ca 2+ -dependent channel currents were inhibited by 10 μ m ZnCl 2 but niflumic acid, an inhibitor of Ca 2+ -activated Cl â channels, had no effect. Inhibition of cGMP-dependent protein kinase activity by the cGMP-dependent protein kinase inhibitor
KT5823 or replacement of ATP by AMP-PNP reduced NP o , while activation of cGMP-dependent protein kinase by guanosine 3â², 5â²-cyclic monophosphate, β-phenyl-1, N 2 -etheno-8-bromo-sodium salt (8Br PET cGMP) produced a significant increase in single channel NP o . It is likely that these single channel currents underlie the noradrenaline-activated inward current important for vasomotion
in these resistance arteries. |
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ISSN: | 0022-3751 1469-7793 |
DOI: | 10.1113/jphysiol.2003.057646 |