Ultrastructure and Development of Heart Wall of Zebrafish (Danio rerio)

Kim, Hyoung Tae; Chon, Sung Eun; Kim, Hue; Lee, Moo Sam

Abstract

Light and electron microscopic obserbations of developing heart wall of zebrafish, which has been recently used for developmental studies of many organs, were performed. Heart tissue was obtained from adult and 24, 48 and 72 hour embryos of zebrafish. Heart wall of adult zebrafish was composed of 3 typical layers, endocardium, myocardium and epicardium, as ones of other vertebrates. Heart wall of 24 hour embryo was composed of primitive myocytes. Myofibrils in myocytes at this period was found as assembly of myofilaments, 500~1,000 nm sized and 5~10 layered. Heart of 48 hour embryo has ventricle and atrium. Ventricular wall of was composed of endocardium, myocardium and incomplete epicardium. Atrial wall at 48 hour embryo was composed of endocardium and myocardium. Development of myocytes in ventricle was earlier than those of atrium, and myofibrils with Z disc were found first at 48 hour embryo. Heart wall of 72 hour embryo was morphologically similar to that of 48 hour embryo, but development of myocytes was more progressed. Specific atrial granules of 100~200 nm size appeared very rarely at 24 hour embryo and its numbers increased gradually at 48 and 72 hour embryos in myocytes of atrium as well as the ventricle. Specific atrial granules were consider as ones containing atrial natriuretic peptide (ANP).