title: Uptake of foreign ferritin in heart of firemouth cichlid (cichlidae: teleostei).
abstract: The ultrastructure of the endothelium in the heart of the firemouth cichlid (Thorichthys meeki) and its capability and capacity to take up foreign ferritin are described. The entire wall in atrium and ventricle was spongy and composed of muscle trabeculae, covered by endothelial cells which were about 4-6-μm thick in atrium and flat in ventricle. These cells contained a number of moderately electron-dense bodies (MDBs, diameter 2 μm and less), clathrin-coated vesicles, and tubules of agranular endoplasmatic reticulum. Numerous yellow-brown granules, width 2 μm and less, occurred in the endocardial endothelium covering the cardiac muscle trabeculae in ferritin-injected firemouth cichlid 8 hr postinjection; much Prussian blue precipitated within these granules when treated with acid ferrocyanide. When the time between the injection and sacrifice was extended to 24 hr, the granules and Prussian blue precipitations in the corresponding endocardial endothelium displayed a width of 3 μm and more. The endocardial endothelium facing the cardiac main lumen or covering the valves and walls of the atrio-ventriclar or ventriculo-bulbar apertures nearly lacks such granules and precipitations as well as MDB, clathrin-coated vesicles and tubules of agranular endoplasmic reticulum, suggesting that the endothelium at these sites is not endocytic. Lipofuscinlike pigments were demonstrated by the Schmorl's technique in the endocardial endothelium covering the heart muscle trabeculae in firemouth cichlid. Together these findings suggest that the endocardial endothelium cover on the muscle trabeculae in heart wall in firemouth cichlid is highly specialized to play important roles in the uptake of scavenger molecules and foreign particles. Such an uptake may be very efficient as this cell layer comes in contact with nearly the entire blood volume throughout the spongy heart wall in this type of teleosts.
authors.affiliation: Faculty of Engineering and Science, Sogn og Fjordane University College, Sogndal, Norway. Ingvar.Leknes@hisf.no
authors.forename: Ingvar Leiv
authors.initials: IL
authors.lastname: Leknes
mesh_terms: D000818:Animals; D023681:Cichlids; D003594:Cytoplasmic Granules / Q000378:metabolism* / Q000648:ultrastructure; D004730:Endothelium, Vascular / Q000378:metabolism* / Q000648:ultrastructure; D005293:Ferritins / Q000378:metabolism*; D006321:Heart / Q000502:physiology*; D009206:Myocardium / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D005293:Ferritins