Zebrafish Heart as a Model System to Study Structure-Function Relationships

Abstract

The zebrafish (Danio rerio) has been intensively used in cardiovascular biology mainly for study of heart development. This is a promising cost-effective model system to study structure-function due to the ease of genetic manipulations. However, the basic contractile physiology of zebrafish heart is still incompletely understood. Moreover, the applicability of the fish heart as a model system for study mammalian heart contractility needs to be established.The aim of our work was to establish the zebrafish as a model system to approach structure-function cardiac myocyte biology. Accordingly, we performed experiments with a focus on the Frank-Starling mechanisms at two levels: cellular (intact cells) and myofilament level (permeabilized cells). In single cell experiments we were able to attach a single enzymatically isolated zebrafish ventricular myocytes to myotak coated carbon probes and measure force, intracellular calcium, cell length, and sarcomere length in electrically paced cells over a range (20%) of cell lengths. In skinned cell experiments, we used a single myofibril technique to measure activation/relaxation kinetics and force-Ca2+ relations at short and long sarcomere lengths (2.2 and 2.4 um). Zebrafish intact myocytes displayed robust length induced increase in twitch force in the absence of calcium transient alteration. In skinned zebrafish muscle we found robust myofilament length dependent activation as well as characteristic activation/relaxation dynamics. We conclude that the zebrafish heart is an appropriate model to study cardiac structure-function relationships.