Morpho-functional characterization of the goldfish (Carassius auratus L.) heart F. Garofalo a, 1 , S. Imbrogno a, 1 , B. Tota a , D. Amelio a, b, ⁎ a Department of Cell Biology, University of Calabria, Italy b Department of Pharmaco-Biology, University of Calabria, Italy abstract article info Article history: Received 23 April 2012 Received in revised form 31 May 2012 Accepted 31 May 2012 Available online 13 June 2012 Keywords: Fish heart Goldfish eNOS Heart morphology Cardiac performance Using morphological and physiological approaches we provided, for the first time, a structural and functional characterization of Carassius auratus L. heart. Besides to the classical four chambers, i.e. sinus venosus, atrium, ventricle, bulbus, we described two distinct structures corresponding to the atrio-ventricular (AV) region and the conus arteriosus. The atrium is very large and highly trabeculated; the ventricle shows an outer compacta, vascularized by coronary vessels, and an inner spongiosa; the bulbus wall is characterized by a high elastin/ collagen ratio, which makes it extremely compliant. Immunolocalization revealed a strong expression of ac- tivated “eNOS-like” isoforms both at coronary endothelium and, to a lesser extent, in the myocardiocytes and the endocardial endothelium (EE). The structural design of the heart appears to comply with its mechanical function. Using an in vitro working heart preparation, cardiac performance was evaluated at different filling and afterload pressures. The hearts were very sensitive to filling pressure increases. Maximum Stroke volume (SV = 1.08 ± 0.09 mL/kg body mass) was obtained with an input pressure of 0.4 kPa. The heart was not able to sustain afterload increases, values higher than 1.5 kPa impairing its performance. These morpho-functional features are consistent with a volume pump mechanical performance. © 2012 Elsevier Inc. All rights reserved. 1. Introduction The fish heart exhibits an impressive morpho-functional flexibility in relation to both developmental and ecophysiological changes. This flexibility, clearly exemplified by the relationships between the myo- architecture of the ventricular pump and its mechanical performance, is an issue of elevated interest in comparative cardiac morphodynamics (Tota and Gattuso, 1996; Cerra et al., 2004). A notable aspect of this car- diac flexibility is highlighted by the relationship between the structural organization of the ventricular pump and the mechanical performance of the heart, evaluated in terms of the relative contribution of pressure and volume work to the stroke work (Tota and Gattuso, 1996). This pro- vides an insight into how the internal construction of the ventricular chamber is adapted to its functional performance. Numerous studies have reviewed the structural organization of the fish heart chambers also in terms of cardiac performance (Santer, 1985; Satchell, 1991; Farrell and Jones, 1992; Burggren et al., 1997). On the basis of the exter- nal shape, fish heart ventricle has been classified into three major cate- gories, i.e. sac-like, which appears rounded and with a blunt apex; tubular, showing a cylindrical cross section; and pyramidal, with a tri- angular base (Santer et al., 1983; Santer, 1985, and references therein). Moreover, the different myocardial arrangement allowed to distinguish four different ventricle type (Tota et al., 1983; Tota, 1989; Farrell and Jones, 1992 and references therein). In the Type I the ventricular myo- cardium appears completely avascular and trabeculated. The Type II presents both an external compacta (vascularized) layer and an inner spongiosa. Ventricles of type III show vessels both in the compacta and spongiosa. Finally, the Type IV includes ventricles prevalently formed by compact vascularized myocardium. Fish of the genus Carassius (Cypriniformes, Cyprinidae) represent advanced forms of teleosts largely used as model organisms in the fields of molecular evolution and comparative genomics (Luo et al., 2006), cell biology (Lee et al., 1997), immunology (Hanington et al., 2006) and neurobiology (Huesa et al., 2005; Preuss et al., 2006). Both the goldfish (Carassius auratus) and the crucian carp (Carassius carassius) are able to tolerate prolonged and severe hypoxic condi- tions and remain active when overwintering in ice-covered ponds (Bickler and Buck, 2007). Obviously, this requires the molecular ma- chinery which sustains myocardial contractility to preserve its func- tion. Also several reptiles, such as the turtles, are surprising in their ability to face acidosis which follows the hypoxic/anoxic conditions. Regardless the similar response, each species faces acidosis by acti- vating different strategies. For example, in the crucian carp and the goldfish, the lactic acidosis which follows the hypoxic/anoxic condi- tions is prevented by converting lactate to ethanol and CO 2 , both ex- creted by the gills (Bickler and Buck, 2007). In this context, the teleost C. auratus has been so far regarded as a precious model to study the mechanisms which allow survival and heart function preservation Comparative Biochemistry and Physiology, Part A 163 (2012) 215–222 ⁎ Corresponding author at: Department of Cell Biology and Pharmaco-Biology, Uni- versity of Calabria, 87030 Arcavacata di Rende, CS, Italy. Tel.: + 39 0984 492909; fax: +39 0984 492906. E-mail address: daniela.amelio@unical.it (D. Amelio). 1 These authors equally contributed to the work. 1095-6433/$ – see front matter © 2012 Elsevier Inc. All rights reserved. doi:10.1016/j.cbpa.2012.05.206 Contents lists available at SciVerse ScienceDirect Comparative Biochemistry and Physiology, Part A journal homepage: www.elsevier.com/locate/cbpa