The heart ofSparus auratus: a reappraisal of cardiac functional morphology in teleosts

Abstract

This morphodynamic study provides an insight on how the architecture of the heart ventricle of the gilthead seabream (Sparus auratus) is designed to accomplish the functional performance typical of an active teleost species. Using an in vitro working heart preparation, mechanical performance was analyzed under loading (i.e., preload and afterload) challenges. The hearts were very sensitive to filling pressure increases. Maximum cardiac output (CO: 55.66+/-4.54 ml/min/kg body weight; mean+/-SEM) and maximum stroke volume (VS: 0.42+/-0.027 ml/kg body weight; mean+/-SEM) were obtained at an input pressure of 1 kPa. When exposed to output pressure (OP) changes, the hearts maintained constant CO and SV up to about 4 kPa; further increases of afterload significantly compromised mechanical performance. Surprisingly, this "athletic" pumping performance was achieved by an entirely trabeculated pyramidal ventricle. The ventricular architecture was characterized by a system of small luminae and trabecular sheets radiating outward from the central lumen. The most peripheral part of the ventricular chamber contained single trabeculae and the corresponding lacunary spaces. The ventricular cavity was bounded by an outer myocardial monolayer "shell" to which the peripheral trabeculae were attached. Myofibril organization differed in the trabeculae and in the outer monolayer. The structural features challenge common beliefs regarding the typical "athletic" teleost heart design.

Cortisol response to stress is associated with myocardial remodeling in salmonid fishes

“…Fibrosis is the dominant histological reaction to injury in the mammalian heart and it adversely increases tissue stiffness and impairs normal cardiac function (Schnitt et al, 1993;Weber et al, 1994). In fish, though, collagen remodeling has been postulated to play an important role in the maintenance of mechanical cardiac performance (Cerra et al, 2004;Icardo et al, 2005). We also found enhanced collagen deposition in the HR ventricles compared with the LR ventricles, as evaluated by AFOG staining.…”

Phospholamban S-nitrosylation modulates Starling response in fish heart

“…This elevated sensitivity of the fish hearts to the Starling response, well documented in both temperate eurytherm and cold-adapted teleosts (gilthead seabream, Icardo et al 2005;eel, Imbrogno et al 2001;icefish, Tota et al 1991), has been in part attributed to a greater myocardial extensibility of the highly trabeculate fish heart, coupled to a maintained increase in myofilament Ca 2þ sensitivity over a large range of sarcomere lengths (Di Maio & Block 2008;Shiels & White 2008).…”

The Teleost Heart: A Morphological Approach

“…The trabecular network has been described as a highly organized system of small lumina and trabecular sheets which radiate outward from a central lumen (Fig. 2.4b ) (Munshi et al 2001 ;Icardo et al 2005b ) . The size of the lumina decreases progressively toward the ventricular periphery.…”

“…The main ventricular lumen would support the highest amount of stress, and the stress would be progressively attenuated toward the periphery. The trabecular sheets would produce enough contractile force, and the communication between the different lumina would facilitate blood squeezing (Icardo et al 2005b ) .…”