A single injection of periostin decreases cardiac voltage-gated Na+ channel in rat ventricles

Figures

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  Fig. 1.. A single injection of periostin (POSTN) decreases peak amplitude, delays time to peak and prolongs repolarization of action potential (AP) in rat ventricular myocytes. POSTN (64 µg/kg) or vehicle (Vehicle) was intravenously injected to rats via right jugular vein. Twenty-four hr after the injection, ventricular myocytes were isolated. Whole-cell patch clamp (current-clamp mode) was performed to measure AP. (A) Representative AP waveform in the ventricular myocytes from POSTN (red) or Vehicle (black) was shown. (B) The resting membrane potential (RMP) and the peak amplitude of AP were measured and shown as mean ± standard error of the mean (S.E.M.). (C) A time to peak of AP was measured and shown as means ± S.E.M. (D) The AP duration at 20%, 50% and 90% repolarization from the peak (APD20, APD50 and APD90) was measured and shown as means ± S.E.M. Vehicle: n=11 (N=6); POSTN: n=12 (N=5). *,**P<0.05, 0.01 vs. Vehicle (unpaired two-tailed Student’s t-test).

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  Fig. 2.. A single injection of periostin (POSTN) decreases Na+ current (INa) and protein expression of cardiac voltage-gated Na+ channel (NaV1.5) in rat ventricular myocytes. POSTN (64 µg/kg) or vehicle (Vehicle) were intravenously injected to rats for 24 hr. (A, B) Whole-cell patch clamp (voltage-clamp mode) was performed to measure INa in ventricular myocytes isolated from the rats. (A) Representative trances of INa in the ventricular myocytes from POSTN (lower) or Vehicle (upper) were shown. Inset: depolarization pulse protocol. (B) Current-voltage curve for peak amplitudes of INa was shown as means ± S.E.M. Vehicle: n=10 (N=6); POSTN: n=10 (N=3). The current (pA) was normalized by cellular membrane capacitance (pF). *P<0.05 vs. Vehicle [unpaired two-tailed Student’s t-test]. (C, D) Western blotting was performed to examine the protein expression of NaV1.5 in ventricles isolated from the rats. (C) Representative blots for NaV1.5 and ponceau S-stained total protein in nitrocellulose membrane were shown. (D) The expression level of NaV1.5 was corrected by ponceau S-stained total protein level, and the normalized expression relative to Vehicle was shown as mean ± S.E.M. Vehicle: N=12;…

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  Fig. 3.. Periostin (POSTN)-treatment decreases Na+ current (INa) and protein expression of cardiac voltage-gated Na+ channel (NaV1.5) in neonatal rat ventricular myocytes (NRVMs). (A, B) NRVMs were stimulated with POSTN (1 µg/ml) or vehicle (Vehicle) for 24 hr. Whole-cell patch clamp (voltage-clamp mode) was performed to measure INa. (A) Representative trances of INa in POSTN (lower) or Vehicle (upper) were shown. Inset: depolarization pulse protocol. (B) Current-voltage curve for the peak amplitudes of INa was shown as means ± S.E.M. [Vehicle (black): n=16; POSTN (red): n=16]. The current (pA) was normalized by cellular membrane capacitance (pF). *P<0.05 vs. Vehicle (unpaired two-tailed Student’s t-test). (C-F) NRVMs were stimulated with POSTN (0.03–3 µg/ml) or vehicle (Cont) for 10 min-24 hr. After the total protein was extracted, Western blotting was performed to examine expression of NaV1.5. (C, E) Representative blots for NaV1.5 and ponceau S-stained total protein in nitrocellulose membrane were shown. (D, F) The expression level of NaV1.5 was corrected by ponceau S-stained total protein level, and the normalized expression relative to Cont was shown as mean ± S.E.M. (n=3). *,…

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  Fig. 4.. Proposed model. A single injection of periostin (POSTN) decreased Na+ current (INa) in isolated ventricular myocytes by suppressing cardiac voltage-gated Na+ channel (NaV1.5) protein expression in rats, which was accompanied by a decrease of peak amplitude and a prolongation of time to peak in action potential (AP) and increase in RS height in electrocardiogram.