Ischemic preconditioning preserves connexin 43 phosphorylation during sustained ischemia in pig hearts in vivo

ABSTRACT During myocardial ischemia, connexin 43 (Cx43) is dephosphorylated in vitro, and the subsequent opening of gap junctions formed by two opposing Cx43 hexamers was suggested to propagate ischemia/reperfusion injury. Reduction of infarct size (IS) by ischemic preconditioning (IP) involves activation of protein kinase C (PKC) and p38 mitogen activated protein kinase (MAPK), both of which can phosphorylate Cx43. We now studied in anesthetized pigs whether IP impacts on Cx43 phosphorylation by measuring the density of non‐phosphorylated and total Cx43 (confocal laser) during normoperfusion and 90‐min ischemia in non‐preconditioned and preconditioned hearts. Co‐localization of PKCα, p38MAPKα, and p38MAPKβ with Cx43 and the activity of p38MAPK were assessed. IP by 10 min ischemia and 15 min reperfusion reduced IS. Non‐phosphorylated Cx43 remained unchanged during ischemia in preconditioned hearts, while it increased from 35±3 to 75±8 AU (P