Key result
Ranolazine attenuated hypoxia- and H2O2-stimulated late sodium current in guinea pig ventricular myocytes by reducing both the open probability and open time of Na-channel late openings.
Ranolazine attenuates hypoxia- and H2O2-induced increases in late sodium current by reducing the open probability and open time of sodium channels.
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Supports preclinical late sodium current research; leaves open translation to human ischemia or oxidative stress.
Ranolazine attenuates cardiac arrhythmic activity associated with hypoxia and hydrogen peroxide (H2O2) by inhibition of late sodium current (late INa). The mechanism of ranolazine's action on Na channels was investigated using whole-cell and single-channel recording from guinea pig isolated ventricular myocytes. Hypoxia increased whole-cell late INa from -0.48 ± 0.02 to -3.99 ± 0.07 pA/pF. Ranolazine at 3 and 9 μmol/L reduced the hypoxia-induced late INa by 16% ± 3% and 55% ± 3%, respectively. Hypoxia increased the mean open probability and open time of Na-channel late openings from 0.016 ± 0.001 to 0.064 ± 0.007 milliseconds and from 0.693 ± 0.043 to 1.081 ± 0.098 milliseconds, respectively. Ranolazine at 3 and 9 μmol/L attenuated the hypoxia-induced increase of open probability by 19% ± 7% and 61% ± 1%, and increase of open time by 26% ± 19% and 74 ± 21%, respectively. H2O2 increased the mean open probability and open time of Na-channel late openings from 0.013 ± 0.002 to 0.107 ± 0.015 milliseconds and from 0.689 ± 0.075 to 1.487 ± 0.072 milliseconds, respectively. Ranolazine at 3 and 6 μmol/L reduced the H2O2-induced increase of mean open probability by 60% ± 7% and 95% ± 2%, and the increase of mean open time by 31% ± 21% and 82% ± 8%. In conclusion, the inhibition by ranolazine of hypoxia- and H2O2-stimulated late INa is due to reduction of both the open probability and open time of Na-channel late openings.
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Ma et al. (2014) studied this question. Ranolazine vs. Hypoxia or H2O2 alone was evaluated on Hypoxia- and H2O2-induced increases in sodium channel late openings. Ranolazine attenuated hypoxia- and H2O2-stimulated late sodium current in guinea pig ventricular myocytes by reducing both the open probability and open time of Na-channel late openings.
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