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Modulation of potassium currents by angiotensin and oxidative stress in cardiac cells from the diabetic rat
Author(s) -
Shimoni Y.,
Hunt D.,
Chuang M.,
Chen K. Y.,
Kargacin G.,
Severson D. L.
Publication year - 2005
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 - 10.1113/jphysiol.2005.090639
Subject(s) - oxidative stress , potassium , angiotensin ii , potassium channel , medicine , oxidative phosphorylation , endocrinology , modulation (music) , chemistry , biophysics , biology , biochemistry , physics , receptor , organic chemistry , acoustics
Diabetes induces oxidative stress and leads to attenuation of cardiac K + currents. We investigated the role of superoxide ions and angiotensin II (ANG II) in generating and linking oxidative stress to the modulation of K + currents under diabetic conditions. K + currents were measured using patch‐clamp methods in ventricular myocytes from streptozotocin (STZ)‐induced diabetic rats. Superoxide ion levels, indicating oxidative stress, were measured by fluorescent labelling with dihydroethidium (DHE). ANG II content was measured using enzyme‐linked immunosorbent asssay (ELISA). The results showed DHE fluorescence to be significantly higher in cells from diabetic males, compared to controls. Relief of stress by the NADPH oxidase inhibitor apocynin or by superoxide dismutase (SOD) but not by catalase reversed the attenuation of K + currents and reduced DHE fluorescence. In cells from diabetic females, neither apocynin nor SOD augmented K + currents, ANG II was not elevated and DHE fluorescence was significantly weaker than in cells from males. Reduced glutathione (GSH) also augmented K + currents in cells from diabetic males but not females. In ovariectomized diabetic females K + currents were augmented by GSH and apocynin. Current augmentation and the attenuation of DHE fluorescence by apocynin were significantly blunted by excess ANG II (300 n m ). Diabetic male rats pretreated with the angiotensin‐converting enzyme (ACE) inhibitor quinapril were hyperglycaemic, but their cellular ANG II levels and DHE fluorescence were significantly decreased. In cells from these rats, K + currents were insensitive to apocynin. In conclusion, diabetes‐related oxidative stress attenuates K + currents through ANG II‐generated increased superoxide ion levels. When ANG II levels are lower, as in diabetic females or following ACE inhibition in males, oxidative stress is reduced, with blunted alterations in K + currents.