Data from: Heterogeneity of t-tubules in pig hearts

Background: T-tubules are invaginations of the sarcolemma that play a key role in excitation-contraction coupling in mammalian cardiac myocytes. Although t-tubules were generally considered to be effectively absent in atrial myocytes, recent studies on atrial cells from larger mammals suggest that t-tubules may be more numerous than previously supposed. However, the degree of heterogeneity between cardiomyocytes in the extent of the t-tubule network remains unclear. The aim of the present study was to investigate the t-tubule network of pig atrial myocytes in comparison with ventricular tissue. Methods: Cardiac tissue was obtained from young female Landrace White pigs (45–75 kg, 5–6 months old). Cardiomyocytes were isolated by arterial perfusion with a collagenase-containing solution. Ca2+ transients were examined in field-stimulated isolated cells loaded with fluo-4-AM. Membranes of isolated cells were visualized using di-8-ANEPPS. T-tubules were visualized in fixed-frozen tissue sections stained with Alexa-Fluor 488-conjugated WGA. Binary images were obtained by application of a threshold and t-tubule density (TTD) calculated. A distance mapping approach was used to calculate half-distance to nearest t-tubule (HDTT). Results & Conclusion: The spatio-temporal properties of the Ca2+ transient appeared to be consistent with the absence of functional t-tubules in isolated atrial myocytes. However, t-tubules could be identified in a sub-population of atrial cells in frozen sections. While all ventricular myocytes had TTD >3% (mean TTD = 6.94±0.395%, n = 24), this was true of just 5/22 atrial cells. Mean atrial TTD (2.35±0.457%, n = 22) was lower than ventricular TTD (P<0.0001). TTD correlated with cell-width (r = 0.7756, n = 46, P<0.0001). HDTT was significantly greater in the atrial cells with TTD ≤3% (2.29±0.16 μm, n = 17) than in either ventricular cells (1.33±0.05 μm, n = 24, P<0.0001) or in atrial cells with TTD >3% (1.65±0.06 μm, n = 5, P<0.05). These data demonstrate considerable heterogeneity between pig cardiomyocytes in the extent of t-tubule network, which correlated with cell size.,Folder 1 - linescansFolder contains linescans in TIF format of the four atrial cells referred to in Figure 1 of the manuscript.Folder 2 - di-8-ANEPPSA folder containing two further folders ('atrial' and 'ventricular'), which contain, respectively, TIF images of the 10 atrial and 4 ventricular di-8-ANEPPS-stained cells referred to in Figure 2.Folder 2 - di-8.7zSham v control TTDA spreadsheet containing t-tubule densities (TTD) of atrial and ventricular cells from Sham and Control animals to establish that there was no difference the t-tubule network in either atrial or ventricular cells between these two groups of animals.Pig TTD A V Sham vs control.xlsxControl atrial 1Original images of sections from atrial tissue from control animals used for analysis presented in Figures 4 - 6. Folder 1 of 5.Control atrial 2Original images of sections of atrial tissue from control animals used for analysis shown in Figures 4 - 6. Folder 2 of 5.Sham atrialOriginal images of atrial sections from Sham animals used for analysis presented in Figures 4 - 6. Folder 3 of 5.Control ventricularOriginal images of ventricular sections from control animals used for analysis presented in Figures 4 - 6. Folder 4 of 5.Sham ventricularOriginal images of sections from ventricular cells from Sham animals used for analysis presented in Figures 4 - 6. Folder 5 of 5.,