Fig. 2.

Effects of glucocorticoid manipulation on development, structure and function of the embryonic heart Structural and functional observations of embryonic hearts were carried over 120 h post fertilization (hpf) using Tg (CMLC2:GFP) zebrafish which had been exposed to the glucocorticoid receptor (GR) agonist dexamethasone (Dex) [100 μM] for 120 h or treated with targeted GR translational blocking morpholino (GR Mo). Results were compared with controls which are a mean of Dex (vehicle only) controls and GR Mo (mism Mo) controls. Parameters investigated were A) Inflow/outflow area (measured at 72 hpf), an indicator of cardiac looping from cardiac tube to two chambered heart, B) ventricular area, a marker of cardiac growth and development, C) cardiomyocyte number normalized to heart length, D) heart rate, E) stroke volume and F) cardiac output. Data are mean ± SEM and were compared to control by one-way ANOVA and Dunnett's post hoc test. A) inflow/outflow distance n = (20 ***p ≤ 0.0001, B) ventricle area n = 4 experiments, (6 hearts per experiment) ± SEM *P ≤ 0.05, **P ≤ 0.001, C) ventricle cardiomyocyte number (normalized to body length) n = 12 hearts *p ≤ 0.05, **p ≤ 0.01. D–F), all cardiac function assessments n = 4 experiments (12 embryos per experiment) *p ≤ 0.05.