New cardiac expression of two adenosine-2A receptor isoforms in dysfunctioning minipigs

Purpose: Eight AR variants are reported in humans while no AR isoforms in pigs. The aim of this study was to evaluate potential isoforms presence in cardiac pig tissue to better define possible involvement of AR in the cardiovascular pathophysiology. Materials and methods: In adult male minipigs (n = 4) left ventricular dysfunction (LVD) was induced by pacing at 200 bpm in the right ventricular (RV) apex. In these animals and in sham operated pigs (C-SHAM, n = 4) cardiac tissue was collected from LV-septal wall (LV-SW)-close to pacing site-and from lateral (opposite) site (LV-OSW). AR specific primers, derived from Sus scrofa AY772412 sequence, were used for Real-Time PCR. The DNA was sequenced using the Sanger method. Histological analysis was also performed. Results: In LV-SW of LVD minipigs the AR melting curves were characterized by a sharp peak between 87 and 91 °C (short isoform, 1-94 bp) on the right of the principal peak corresponding to a long AR isoform (GenBank: JQ229674.1) 1-213 bp. As for C-SHAM only one peak was observed in LV-OSW region of LVD animals. The short isoform had an alternative promoter region and a specific translated protein. Histology showed in LVD-LV-SW prominent Purkinje cells compared to LV-OSW and C-SHAM. No difference in AR expression was observed between LVD animals and C-SHAM although a slight decrease was observed in LVD-LV-OSW. Conclusions: The presence of two different isoforms in the myocardium close to the insertion of pacing is suggestive of a differential state-specific expression of AR in cardiac tissue.