OBJECTIVE: Heterogeneity of action potential configuration in the left ventricle (LV), and the contribution of M cells to it, has been observed in the human heart and is important for arrhythmogenesis. Whether the pig heart has similar properties remains a controversial but important issue as the pig heart is currently under study for use in xenotransplantation. METHODS: Single myocytes were enzymatically isolated from the epicardium (EPI, ncells = 29), midmyocardium (MID, ncells = 38), and endocardium (ENDO, ncells = 13) of the free LV wall (npigs = 26, 14-22 weeks old, 55-80 kg), and studied at different stimulation rates during whole-cell recording (normal Tyrode's solution, K(+)-aspartate-based pipette solution, 50 microM K5fluo-3 as [Ca2+]i indicator, 37 degrees C). Standard six-lead ECGs were recorded from anesthetized pigs. RESULTS: The action potential duration (APD) was not significantly different at 0.25 Hz vs. 2 Hz for the majority of cells in all three layers. However, a subpopulation of cells behaved like M cells and had a very steep frequency response (APD90 at 0.25 Hz 538 +/- 30 ms, vs. 337 +/- 9 ms at 2 Hz, P < 0.05, n = 22). These cells were found predominantly in the MID layer (34% of cells), but also (24%) in EPI. M cells had a more pronounced spike-and-dome configuration, with a significantly larger phase 1 magnitude and plateau voltage. The frequency response of these parameters was different from the other cell types. [Ca2+]i transients tended to be larger in M cells. For the in vivo ECG of anesthetized pigs, the QT time was close to the APD90 of M cells, and J waves were seen in 7/12 recordings. CONCLUSIONS: In young adult pigs, M cells can be identified by a steep frequency response of the APD and by a spike-and-dome configuration. These cells are mostly, but not exclusively, found in the midmyocardium, and could contribute to the ECG characteristics. Their properties may however be different from those of other species, including humans.
OBJECTIVE: Heterogeneity of action potential configuration in the left ventricle (LV), and the contribution of M cells to it, has been observed in the human heart and is important for arrhythmogenesis. Whether the pig heart has similar properties remains a controversial but important issue as the pig heart is currently under study for use in xenotransplantation. METHODS: Single myocytes were enzymatically isolated from the epicardium (EPI, ncells = 29), midmyocardium (MID, ncells = 38), and endocardium (ENDO, ncells = 13) of the free LV wall (npigs = 26, 14-22 weeks old, 55-80 kg), and studied at different stimulation rates during whole-cell recording (normal Tyrode's solution, K(+)-aspartate-based pipette solution, 50 microM K5fluo-3 as [Ca2+]i indicator, 37 degrees C). Standard six-lead ECGs were recorded from anesthetized pigs. RESULTS: The action potential duration (APD) was not significantly different at 0.25 Hz vs. 2 Hz for the majority of cells in all three layers. However, a subpopulation of cells behaved like M cells and had a very steep frequency response (APD90 at 0.25 Hz 538 +/- 30 ms, vs. 337 +/- 9 ms at 2 Hz, P < 0.05, n = 22). These cells were found predominantly in the MID layer (34% of cells), but also (24%) in EPI. M cells had a more pronounced spike-and-dome configuration, with a significantly larger phase 1 magnitude and plateau voltage. The frequency response of these parameters was different from the other cell types. [Ca2+]i transients tended to be larger in M cells. For the in vivo ECG of anesthetized pigs, the QT time was close to the APD90 of M cells, and J waves were seen in 7/12 recordings. CONCLUSIONS: In young adult pigs, M cells can be identified by a steep frequency response of the APD and by a spike-and-dome configuration. These cells are mostly, but not exclusively, found in the midmyocardium, and could contribute to the ECG characteristics. Their properties may however be different from those of other species, including humans.
Authors: Gergely Szabó; Norbert Szentandrássy; Tamás Bíró; Balázs I Tóth; Gabriella Czifra; János Magyar; Tamás Bányász; András Varró; László Kovács; Péter P Nánási Journal: Pflugers Arch Date: 2005-06-11 Impact factor: 3.657
Authors: Nan Wang; Marijke De Bock; Gudrun Antoons; Ashish K Gadicherla; Mélissa Bol; Elke Decrock; William Howard Evans; Karin R Sipido; Feliksas F Bukauskas; Luc Leybaert Journal: Basic Res Cardiol Date: 2012-10-21 Impact factor: 17.165
Authors: Young Keun Ahn; Jung Min Ryu; Hea Chang Jeong; Yun Hyeon Kim; Myung Ho Jeong; Min Young Lee; Sang Hun Lee; Jae Hong Park; Seung Pil Yun; Ho Jae Han Journal: J Vet Sci Date: 2008-06 Impact factor: 1.672