Angiotensin II and morpho-functional remodelling of the eel heart

The octapeptide angiotensin II (Ang II), principal effector of the renin–angiotensin system (RAS), is involved in various biological actions including short-term modulation and long-term adaptations. In the eel, Ang II elicits a short-term cardio-modulatory effect. However, information regarding the influence of Ang II on cardiac remodelling is lacking. To fulfil this gap, we used freshwater eels (Anguilla anguilla) intraperitoneally injected for 30 days with Ang II (0.4 or 1.2 nmol g BW-1) or with Ang II (1.2 nmol g BW-1) plus the AT2 receptor antagonist CGP42112. Using an in vitro working heart preparation, cardiac performance was evaluated under loading (i.e. preload and afterload) challenges hearts of all groups showed similar Frank–Starling responses. However, in response to afterload increases, stroke volume rapidly decreased in control hearts, while it was better maintained in Ang II-treated counterparts. These effects were abolished by an antagonist of the AT2 receptor, whose cardiac expression was revealed by western blotting analysis. We also found by immunolocalization and immunoblotting that Ang II influences both expression and localization of molecules involved in cell growth and apoptosis, such as c-kit, apoptosis repressor with CARD domain (ARC), heat shock protein 90 (Hsp90), and endothelial nitric oxide synthase ‘(eNOS)-like’ isoform. These results point to a role of Ang II in eel heart remodelling, providing new insights regarding the modulation of cardiac plasticity in fish