title: Occurrence of heparin in the invertebrate styela plicata (Tunicata) is restricted to cell layers facing the outside environment. An ancient role in defense?
abstract: Heparin is an intracellular product of vertebrate mast cell currently used as exogenous anticoagulant. Despite of the potent biological activities of exogenous heparin, its physiological function has not been clearly established yet. Here, a heparin with similar structure and anticoagulant properties to the mammalian counterpart was shown to occur as the intracellular product of test cells, a cell monolayer that surrounds egg of the invertebrate Styela plicata (Chordata-Tunicata). As in the case of mammalian mast cells, heparin from the ascidian test cells is removed from the intracellular granules after incubation with compound 48/80. Following fertilization, the test cells surrounding the developing larva still retain heparin as metachromatic granulation. In the adult invertebrate, heparin occurs as intracellular granules at the apical tip of epithelial cells surrounding the lumen of both intestine and pharynx, in close contact with the external environment. This is the first description of the presence of heparin in cytoplasmic granules of epithelial-like cells around the lumen of sites exposed to external agents. This arrangement may reflect the participation of heparin in defense mechanisms in this invertebrate.
authors.affiliation: Laboratório de Tecido Conjuntivo, Hospital Universitário Clementino Fraga Filho and Departamento de Bioquimica Médica, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Caixa Postal 68041, Rio de Janeiro 21.
authors.forename: M C
authors.initials: MC
authors.lastname: Cavalcante
authors.forename: S
authors.initials: S
authors.lastname: Allodi
authors.forename: A P
authors.initials: AP
authors.lastname: Valente
authors.forename: A H
authors.initials: AH
authors.lastname: Straus
authors.forename: H K
authors.initials: HK
authors.lastname: Takahashi
authors.forename: P A
authors.initials: PA
authors.lastname: Mourão
authors.forename: M S
authors.initials: MS
authors.lastname: Pavão
mesh_terms: D000818:Animals; D000925:Anticoagulants / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology; D015550:Cell Degranulation; D002851:Chromatography, High Pressure Liquid; D004187:Disaccharides / Q000737:chemistry; D005455:Fluorescent Antibody Technique; D006493:Heparin / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism* / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D010063:Ovum / Q000737:chemistry / Q000166:cytology; D010614:Pharynx / Q000378:metabolism; D011133:Polysaccharide-Lyases / Q000378:metabolism; D022142:Secretory Vesicles / Q000378:metabolism; D014561:Urochordata / Q000737:chemistry* / Q000166:cytology*
chemical_list: D000925:Anticoagulants; D004187:Disaccharides; D006493:Heparin; D011133:Polysaccharide-Lyases; C021349:heparitinsulfate lyase