Cardiac morphology and blood pressure in the adult zebrafish

Zebrafish has become a popular model for the study of cardiovascular develo pment. We performed morphologic analysis on 3 months postfertilization zebr afish hearts (n greater than or equal to 20) with scanning electron microsc opy, hematoxylin and eosin staining and Masson's trichrome staining, and mo rphometric analysis on cell organelles with transmission electron photomicr ographs. We measured atrial, ventricular, ventral, and dorsal aortic blood pressures (n greater than or equal to 5) with a servonull system. The atrio ventricular orifice was positioned on the dorsomedial side of the anterior ventricle, surmounted by the single-chambered atrium. The atrioventricular valve was free of tension apparati but supported by papillary bands to prev ent retrograde flow. The ventricle was spanned with fine trabeculae perpend icular to the compact layer and perforated with a subepicardial network of coronary arteries, which originated from the efferent branchial arteries by means of the main coronary vessel. Ventricular myocytes were larger than t hose in the atrium P < 0.05) with abundant mitochondria close to the sarcol emmal. Sarcoplasmic reticulum was sparse in zebrafish ventricle. Bulbus art eriosus was located anterior to the ventricle, and functioned as an elastic reservoir to absorb the rapid rise of pressure during ventricular contract ion. The dense matrix of collagen interspersed across the entire bulbus art eriosus exemplified the characteristics of vasculature smooth muscle. There were pressure gradients from atrium to ventricle, and from ventral to dors al aorta, indicating that the valves and the branchial arteries, respective ly, were points of resistance to blood flow. These data serve as a framewor k for structure-function investigations of the zebrafish cardiovascular sys tem. Anat Rec 264:1-12, 2001. (C) 2001 Wiley-Liss, Inc.