To determine whether Ca<sup>2+</sup> activated Cl<sup>-</sup>current (I<sub>Cl(Ca)</sub>) contributes to the functional remodeling of the failing heart. Methods Whole cell patch-c...To determine whether Ca<sup>2+</sup> activated Cl<sup>-</sup>current (I<sub>Cl(Ca)</sub>) contributes to the functional remodeling of the failing heart. Methods Whole cell patch-clamp recording technique was employed to record the I<sub>Cl(Ca)</sub> in cardiac myocytes enzymatically isolated from rapidly pacing induced canine failing hearts at room temperature and compared that of the normal hearts (Nor).Results The current density of DIDS (200M) sensitive I<sub>Cl(Ca)</sub> induced by intracellular Ca<sup>2+</sup> release trigged by L-type Ca<sup>2+</sup> current (I<sub>Ca,L</sub>) was significantly decreased in heart failare (HF) cells compared to Nor cells.At membrane voltage of 20mV,the I<sub>Cl(Ca)</sub> density was 3.02±0. 54 pA/pF in Nor (n=6) vs.1.31±0.25 pA/pF in HF (n=8) cells,(P【0.01),while the averaged I<sub>Ca,L</sub> density did not show difference between two groups.The time constant of current decay of I<sub>Cl(Ca)</sub> was similar in both types of cells.On the other hand,in intra cellular Ca<sup>2+</sup> clamped mode,where the [Ca<sup>2+</sup>]<sub>i</sub> was maintained at 100nmol/L,I<sub>Cl(Ca)</sub> density be increased significantly in HF cells when the membrane voltage at +30mV or higher.Conclusions Our results suggest that I<sub>Cl(Ca)</sub> density was decreased in pacing induced failing heart but the channel function be enhanced.Impaired Ca<sup>2+</sup> handing in HF cells rather than reduced I<sub>Cl(Ca)</sub> channel function itself may have caused this abnormality.The I<sub>Cl(Ca)</sub> density reduction might contribute to the prolongation of action potential in failing heart.The I<sub>Cl(Ca)</sub> channel function up-regulation is likely to cause cardiac arrhythmia by inducing a delayed after depolarization,when Ca<sup>2+</sup> overload occurred in diastolic failing heart cells.展开更多
文摘To determine whether Ca<sup>2+</sup> activated Cl<sup>-</sup>current (I<sub>Cl(Ca)</sub>) contributes to the functional remodeling of the failing heart. Methods Whole cell patch-clamp recording technique was employed to record the I<sub>Cl(Ca)</sub> in cardiac myocytes enzymatically isolated from rapidly pacing induced canine failing hearts at room temperature and compared that of the normal hearts (Nor).Results The current density of DIDS (200M) sensitive I<sub>Cl(Ca)</sub> induced by intracellular Ca<sup>2+</sup> release trigged by L-type Ca<sup>2+</sup> current (I<sub>Ca,L</sub>) was significantly decreased in heart failare (HF) cells compared to Nor cells.At membrane voltage of 20mV,the I<sub>Cl(Ca)</sub> density was 3.02±0. 54 pA/pF in Nor (n=6) vs.1.31±0.25 pA/pF in HF (n=8) cells,(P【0.01),while the averaged I<sub>Ca,L</sub> density did not show difference between two groups.The time constant of current decay of I<sub>Cl(Ca)</sub> was similar in both types of cells.On the other hand,in intra cellular Ca<sup>2+</sup> clamped mode,where the [Ca<sup>2+</sup>]<sub>i</sub> was maintained at 100nmol/L,I<sub>Cl(Ca)</sub> density be increased significantly in HF cells when the membrane voltage at +30mV or higher.Conclusions Our results suggest that I<sub>Cl(Ca)</sub> density was decreased in pacing induced failing heart but the channel function be enhanced.Impaired Ca<sup>2+</sup> handing in HF cells rather than reduced I<sub>Cl(Ca)</sub> channel function itself may have caused this abnormality.The I<sub>Cl(Ca)</sub> density reduction might contribute to the prolongation of action potential in failing heart.The I<sub>Cl(Ca)</sub> channel function up-regulation is likely to cause cardiac arrhythmia by inducing a delayed after depolarization,when Ca<sup>2+</sup> overload occurred in diastolic failing heart cells.