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Effects of thyroid hormone on the arrhythmogenic activity of pulmonary vein cardiomyocytes

Yao-Chang Chen, MSc^*, Shih-Ann Chen, MD, FACC, Yi-Jen Chen, MD^,*, Mau-Song Chang, MD, Paul Chan, MD, FACC and Cheng-I. Lin, PhD^*

^* Department of Biomedical Engineering and Institute of Pharmacology, National Defense Medical Center, Taipei, Taiwan, Republic of China
Division of Cardiology, Veterans General Hospital-Taipei and Institute of Clinical Medicine, National Yang-Ming University School of Medicine, Taipei, Taiwan, Republic of China
Taipei Medical University Wan-Fang Hospital, Taipei, Taiwan, Republic of China

View larger version (12K): [in a new window]   Figure 1 Effects of thyroid hormone on the occurrence of early after depolarization in a pulmonary vein beating cardiomyocyte. The cell has a rapid spontaneous activity (2 Hz) with oscillation during plateau phase (arrows).

View larger version (8K): [in a new window]   Figure 2 Effects of thyroid hormone on the occurrence of delayed afterdepolarization (DAD) in a pulmonary vein beating cardiomyocyte. During electrical stimuli of 0.1 Hz, there were two DAD after complete repolarization. Arrows indicate the occurrence of DAD.

View larger version (14K): [in a new window]   Figure 3 Effects of thyroid hormone on the action potential (AP) duration of a pulmonary vein (PV) non-beating cardiomyocyte driven electrically at a rate of 0.1 Hz. There was a shorter AP duration at 50% repolarization and at 90% repolarization in the hyperthyroid (A) than there was in the control PV cardiomyocyte (B).

View larger version (19K): [in a new window]   Figure 4 Membrane currents of a hyperthyroid (A) and a control (B) pulmonary vein (PV) cardiomyocyte. The ionic currents were elicited on depolarization from –40 mV to +60 mV. The inset shows the various clamp protocols. The hyperthyroid and control PV cardiomyocytes had similar electrical capacitance. C and D show the measured current-voltage curves of the two cells. The overall transient outward (Ito) and the steady state outward currents (Ik) were indicated by circles and triangles, respectively.

View larger version (18K): [in a new window]   Figure 5 Recording of transient inward currents in a hyperthyroid (A) and a control (B) pulmonary vein (PV) beating cardiomyocyte. The cardiomyocytes were depolarized from –40 mV to +40 mV for 3 s and then repolarized to –40 mV. The transient inward currents were indicated by upward arrows. The inset shows the various clamp protocols. The hyperthyroid and control PV cardiomyocytes had similar electrical capacitance.

View larger version (16K): [in a new window]   Figure 6 Membrane currents of a hyperthyroid (A) and a control (B) pulmonary vein (PV) cardiomyocyte. The ionic currents were elicited from a holding potential of –40 mV to test potentials ranging from –20 mV to –120 mV. The inset shows the various clamp protocols. C shows the measured current-voltage curves of the two cells. The hyperthyroid and control PV cardiomyocytes had similar electrical capacitance.