Figure 2.

Immunofluorescence Images of Cx43 and Cadherin Staining in the Epicardial and Endocardial Regions of Sham-Paced and Paced Hearts. Cx43 immunosignal area is higher in the endocardium than the epicardium in sham-paced hearts (Panels A and B). In the paced hearts, Cx43 immunosignal area is decreased specifically at the endocardium, thereby eliminating the gradient of endocardial to epicardial Cx43 immunosignal area seen in the sham-paced hearts (Panels C and D). Cadherin staining pattern and area is unchanged in the paced hearts (Panels E-H). Co-localization of Cx43 and cadherin immunosignal, as demonstrated by the merged images, is statistically unchanged in the paced hearts compared to sham-paced controls (Panels I-L). Quantification of Cx43 immunosignal area shows an increasing epicardial-to-endocardial gradient in the sham but not in the paced mice, due to decreased signal area specifically in the epicardial region of the paced mice (Panel M). Average Cx43 gap junction (GJ) plaque size appears to increase from epicardium to endocardium in sham but not paced mice, although these differences were not statistically significant (Panel N). There were no significant differences in the number of Cx43 GJ plaques per high power field in epicardial vs. endocardial segments of sham and paced mice (Panel O). Cx43 immuno-staining pattern appeared similar at the RV apex of sham (Panel P) and paced hearts (Panel Q). RV epicardial surface is denoted by asterisks. Epi, epicardial region; Endo, endocardial region.