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Reduced Ca2+ transport across sarcolemma but enhanced spontaneous activity in cardiomyocytes isolated from left atrium-pulmonary veins tissue of myopathic hamster.

Loh YX, Wu KH, Chen YC, Hsu CH, Wei J, Lin CI - J. Biomed. Sci. (2009)

Bottom Line: Myopathic myocytes have shorter AP duration (APD) with smaller ICa,L and INCX than the healthy control.The currents ITO, IK, IK1 and ICa,T are not significantly different in myopathic versus healthy cells.Also, they show altered electrophysiologic properties, which may be due to abnormal Ca2+ channels and may account for contractile dysfunction.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Physiology, National Defense Medical Center, Taipei, Taiwan, ROC. ryanoine@yahoo.com.tw

ABSTRACT

Background: Several lines of evidence point to a particularly important role of the left atrium (LA) in initiating and maintaining atrial fibrillation (AF). This role may be related to the location of pulmonary veins (PVs) in the LA. The aim of the present study was to investigate the action potential (AP) and ionic currents in LA-PV cardiomyocytes isolated from Bio14.6 myopathic Syrian hamsters (36-57 week-old) versus age-matched F1B healthy control hamsters.

Methods and results: Whole-cell patch-clamp techniques were used to record AP in current-clamp mode and ionic currents in voltage-clamp mode. The results obtained show that in both healthy and myopathic LA-PV tissue spontaneously discharging cardiomyocytes can be found, but they are more numerous in myopathic (9/29) than in healthy hamsters (4/42, p < 0.05 by chi2 analysis). Myopathic myocytes have shorter AP duration (APD) with smaller ICa,L and INCX than the healthy control. The currents ITO, IK, IK1 and ICa,T are not significantly different in myopathic versus healthy cells.

Conclusions: Our results indicate that in myopathic Syrian hamsters LA-PV cardiomyocytes are more prone to automatic rhythms. Also, they show altered electrophysiologic properties, which may be due to abnormal Ca2+ channels and may account for contractile dysfunction.

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Triggered rhythms in hamster LA-PV cardiomyocyte. Panel A and B show typical examples of early and delayed afterdepolarization (EAD and DAD, respectively) recorded in a myopathic myocyte stimulated at a rate of 1 Hz in normal Tyrode's solution.
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Figure 3: Triggered rhythms in hamster LA-PV cardiomyocyte. Panel A and B show typical examples of early and delayed afterdepolarization (EAD and DAD, respectively) recorded in a myopathic myocyte stimulated at a rate of 1 Hz in normal Tyrode's solution.

Mentions: Triggered rhythms (EAD and DAD) in myopathic LA-PV cardiomyocytes driven at 1 Hz are shown in Figure 3. EAD were present in 5 out of 29 (17%) myopathic and in 4 out of 42 (10%) healthy LA-PV cardiomyocytes. The incidence of DAD was 2/29 (7%) and 8/42 (19%) in myopathic and healthy myocytes, respectively. There were no significant differences in the incidence of EAD and DAD between the two groups. However, it is not readily apparent why EADs and DADs should be present in both normal and myopathic cells.


Reduced Ca2+ transport across sarcolemma but enhanced spontaneous activity in cardiomyocytes isolated from left atrium-pulmonary veins tissue of myopathic hamster.

Loh YX, Wu KH, Chen YC, Hsu CH, Wei J, Lin CI - J. Biomed. Sci. (2009)

Triggered rhythms in hamster LA-PV cardiomyocyte. Panel A and B show typical examples of early and delayed afterdepolarization (EAD and DAD, respectively) recorded in a myopathic myocyte stimulated at a rate of 1 Hz in normal Tyrode's solution.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2812440&req=5

Figure 3: Triggered rhythms in hamster LA-PV cardiomyocyte. Panel A and B show typical examples of early and delayed afterdepolarization (EAD and DAD, respectively) recorded in a myopathic myocyte stimulated at a rate of 1 Hz in normal Tyrode's solution.
Mentions: Triggered rhythms (EAD and DAD) in myopathic LA-PV cardiomyocytes driven at 1 Hz are shown in Figure 3. EAD were present in 5 out of 29 (17%) myopathic and in 4 out of 42 (10%) healthy LA-PV cardiomyocytes. The incidence of DAD was 2/29 (7%) and 8/42 (19%) in myopathic and healthy myocytes, respectively. There were no significant differences in the incidence of EAD and DAD between the two groups. However, it is not readily apparent why EADs and DADs should be present in both normal and myopathic cells.

Bottom Line: Myopathic myocytes have shorter AP duration (APD) with smaller ICa,L and INCX than the healthy control.The currents ITO, IK, IK1 and ICa,T are not significantly different in myopathic versus healthy cells.Also, they show altered electrophysiologic properties, which may be due to abnormal Ca2+ channels and may account for contractile dysfunction.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Physiology, National Defense Medical Center, Taipei, Taiwan, ROC. ryanoine@yahoo.com.tw

ABSTRACT

Background: Several lines of evidence point to a particularly important role of the left atrium (LA) in initiating and maintaining atrial fibrillation (AF). This role may be related to the location of pulmonary veins (PVs) in the LA. The aim of the present study was to investigate the action potential (AP) and ionic currents in LA-PV cardiomyocytes isolated from Bio14.6 myopathic Syrian hamsters (36-57 week-old) versus age-matched F1B healthy control hamsters.

Methods and results: Whole-cell patch-clamp techniques were used to record AP in current-clamp mode and ionic currents in voltage-clamp mode. The results obtained show that in both healthy and myopathic LA-PV tissue spontaneously discharging cardiomyocytes can be found, but they are more numerous in myopathic (9/29) than in healthy hamsters (4/42, p < 0.05 by chi2 analysis). Myopathic myocytes have shorter AP duration (APD) with smaller ICa,L and INCX than the healthy control. The currents ITO, IK, IK1 and ICa,T are not significantly different in myopathic versus healthy cells.

Conclusions: Our results indicate that in myopathic Syrian hamsters LA-PV cardiomyocytes are more prone to automatic rhythms. Also, they show altered electrophysiologic properties, which may be due to abnormal Ca2+ channels and may account for contractile dysfunction.

Show MeSH
Related in: MedlinePlus