Ischaemia-induced temporal expression of connexin43 in rat heart

To investigate the regulation of cell-to-cell coupling in myocardial ischaemia, the three-dimensional expression of connexin43 (Cx43) during experimental ischaemia was examined using a confocal laser scanning microscope. After induction of myocardial infarction in rats, serial optical sections were obtained from the left ventricular myocardium at various times (3 h to 60 days after ligation). The expression of Cx43 was detected immunohistochemically with FITC-labelled anti-rat Cx43 antibody. Fluorescent dots of Cx43 remained along the intercalated disc and decreased in number around the infarct up to 12 h after ligation. Cx43-expression disappeared completely within 48 h after ligation. After day 4, and especially on days 8 and 15 after ligation, the edges of the cardiomyocytes bordering the infarcted area manifested numerous sarcoplasmic tentacles that reacted positively to anti-desmin antibody. Distinct expression of Cx43 was observed extensively on the tentacles, although no cardiomyocytes remained viable around them. By day 60 after ligation, atypical expression of Cx43 had disappeared. These findings suggest that ischaemia induces temporally abnormal expression of Cx43, which might be responsible for abnormal conduction around the infarct.