Abstract 1086: Electric-field Induced Modulation of Localized Connexin43 Phosphorylation
Background: Connexin43 (Cx43) is a major gap-junctional phosphoprotein in the ventricular myocardium. Its expression, distribution and regulation determine the electrical coupling among cardiomyocytes. Alteration in Cx43-phosphorylation state, which increase tissue anisotropy can be arrhythmogenic. The effects of altered localized electrical field excitation on the Cx43-phosphorylation state have not been established.
Methods: Isolated adult-male rat heart model was used (n=8). Pacing electrode (1.1Fr) was positioned in the endocardial apical region of the right ventricle. Hearts were paced for three hours at a rate of 330bpm, using stimuli of 1.5V and 5msec. Immunoblotting and immunohistochemistry (Serine specific [Ser368] anti-Cx43 and anti-phospho-Serine antibodies) assays were used to quantify the phosphorylation state of Cx43 and map its regional distribution.
Results: Myocardial tissue immunofluorescence of the region (diameter <100μm) surrounding the stimulating electrode showed a consistent increase in the level of dephosphorylation of Cx43 (Dephospho-Cx43) compared to that found in the more remote regions. Phosphorylated Cx43 (Phospho-Cx43) was mainly localized to intercalated disks. Dephospho-Cx43 was diffusely distributed along the cell perimeter. In control hearts (n=4), Cx43 was found to be predominantly phosphorylated. Western blotting densitometry revealed that the ratio of Phospho-Cx43/Dephospho-Cx43 was markedly lower in the paced (4.20 ± 0.18) than in the control hearts (6.25 ± 0.66, p=0.024).
Conclusion: Focal electrical stimulation markedly alters the localized distribution and phosphorylation state of Cx43. These data suggest that localized non-physiological electrical excitation can alter the spatial distribution of Cx43 and its phospho/dephospho balance, and thereby disturb the normal gap-junction dependent cell-cell coupling, creating a potential substrate for anisotropic circuit reentry.