Distinctive sodium and calcium regulation associated with sex differences in atrial electrophysiology of rabbits.

Sex and sodium/calcium regulation play critical roles in cardiac electrophysiology and atrial arrhythmogenesis. We investigated whether sodium and calcium contributed to sex differences in atrial electrophysiology. Whole-cell patch clamp techniques and the indo-1 fluorometric ratio technique were used to investigate the ionic current and intracellular calcium in single isolated male and female rabbit myocytes from the left atrium posterior wall (LAPW) and right atrium (RA). Female LAPW (n=95) and RA (n=49) myocytes had larger cell widths (15.1±0.4 vs. 13.8±0.4 μm, p<0.05; 14.9±0.6 vs. 13.5±0.4 μm, p<0.05) than male LAPW (n=142) and RA (n=57) myocytes. Male LAPW myocytes (n=26) had a higher incidence (57 vs. 16%, p<0.05) of delayed afterdepolarizations (DADs) than female LAPW myocytes (n=24) but there were similar incidences (20 vs. 20%, p>0.05) of DADs in male and female RA myocytes. The late sodium current, calcium transients, and sarcoplasmic reticulum calcium contents were larger in male than female LAPW myocytes but were similar in male and female RA myocytes. However, the ICa-L and nickel-sensitive sodium/calcium exchanger currents were similar between two groups. Different from those in female myocytes, ouabain (10 μM) only induced repeated atrial beats (0 to 45%, p<0.05) in male myocytes (n=11). Moreover, ranolazine (3 μM) perfusion (4.5±0.6 vs. 1 min, p<0.05) was required to decrease the amplitude of DADs in male but not female LAPW myocytes. Increased late sodium currents and calcium contents may contribute to higher arrhythmogenesis in male LAPW myocytes.

Tsai WC ，Chen YC ，Kao YH ，Lu YY ，Chen SA ，Chen YJ ... -  《-》

[Characteristics of electrophysiology and effects of ouabain on transient outward potassium current and L-type calcium current of left atrium posterior wall in rabbits].

Wang T ，Huang CX ，Jiang H ，Tang QZ ，Yang B ，Li GS ... -  《-》

Discrepant electrophysiological characteristics and calcium homeostasis of left atrial anterior and posterior myocytes.

Suenari K ，Chen YC ，Kao YH ，Cheng CC ，Lin YK ，Chen YJ ，Chen SA ... -  《-》

Excavatolide B Modulates the Electrophysiological Characteristics and Calcium Homeostasis of Atrial Myocytes.

Hwang HR ，Tai BY ，Cheng PY ，Chen PN ，Sung PJ ，Wen ZH ，Hsu CH ... -  《-》

Heart failure enhanced pulmonary vein arrhythmogenesis and dysregulated sodium and calcium homeostasis with increased calcium sparks.

Late sodium currents and intracellular Ca(2+) (Ca(2+) (i)) dynamics play an important role in arrhythmogenesis of pulmonary vein (PV) and heart failure (HF). It is not clear whether HF enhances PV arrhythmogenesis through modulation of Ca(2+) homeostasis and increased late sodium currents. The aim of this study was to investigate the sodium and calcium homeostasis in PV cardiomyocytes with HF. Whole-cell patch clamp was used to investigate the action potentials and ionic currents in isolated rabbit single PV cardiomyocytes with and without rapid pacing induced HF. The Ca(2+) (i) dynamics were evaluated through fluorescence and confocal microscopy. As compared to control PV cardiomyocytes (n = 18), HF PV cardiomyocytes (n = 13) had a higher incidence of delayed afterdepolarization (45% vs 13%, P < 0.05) and faster spontaneous activity (3.0 ± 0.2 vs 2.1 ± 0.2 Hz, P < 0.05). HF PV cardiomyocytes had increased late Na(+) currents, Na(+) /Ca(2+) exchanger currents, and transient inward currents, but had decreased Na(+) currents or L-type calcium currents. HF PV cardiomyocytes with pacemaker activity had larger Ca(2+) (i) transients (R410/485, 0.18 ± 0.04 vs 0.11 ± 0.02, P < 0.05), and sarcoplasmic reticulum Ca(2+) stores. Moreover, HF PV cardiomyocytes with pacemaker activity (n = 18) had higher incidence (95% vs 70%, P < 0.05), frequency (7.8 ± 3.1 vs 2.3 ± 1.2 spark/mm/s, P < 0.05), amplitude (F/F(0) , 3.2 ± 0.8 vs 1.9 ± 0.5, P < 0.05), and longer decay time (65 ± 3 vs 48 ± 4 ms, P < 0.05) of Ca(2+) sparks than control PV cardiomyocytes with pacemaker activity (n = 18). Dysregulated sodium and calcium homeostasis, and enhanced calcium sparks promote arrhythmogenesis of PV cardiomyocytes in HF, which may play an important role in the development of atrial fibrillation.

Chang SL ，Chen YC ，Yeh YH ，Lin YK ，Wu TJ ，Lin CI ，Chen SA ，Chen YJ ... -  《-》