Introduction: Cell-to-cell coupling at the connexin-43 (Cx-43) channels is important for metabolic coupling as well as for direct intercellular communication in the heart. Intercellular channels can be modulated by numerous factors, like radiation, to which expression of Cx-43 in mammalian cells is highly sensitive.

Purpose: Our purpose was to explore the effect of a single dosage irradiation on myocardial Cx-43 as well as PKC signaling and whether miRNA-1, which affects GJA1 gene transcription for Cx-43, is implicated.

Methods: Adult, male Wistar rats were subjected to single irradiation at 25 Gy. Six weeks later the hearts were excised from anaesthetized animals. Left ventricular tissue (LV) was used for immunobloting of Cx-43 and PKC. Level of miRNA-1 was quantified by real-time PCR.

Results: In irradiated rats compared to controls the body and heart mass were decreased. Compared to untreated animals disordered cardiomyocyte distribution of Cx-43 positive gap junctions was found due to irradiation. Total Cx-43 expression and its functional phosphorylated forms were significantly increased in LV of rats exposed to irradiation. On the other hand, miRNA-1 expression was significantly decreased in those animals. Furthermore, expression of both PKC-epsilon and PKC-delta was increased in left ventricle of rats exposed to irradiation. PKC-epsilon directly phosphorylates Cx-43 while the latter is implicated in pro-apoptotic signaling.

Conclusions: Our findings indicate that single dose irradiation results in compensatory up-regulation of myocardial Cx-43 via reduced expression of miRNA-1 as well as enhancement of pro-surviving PKC signaling.