title: Tilapia (Oreochromis niloticus) vitellogenins: development of homologous and heterologous ELISAs and analysis of vitellogenin pathway through the ovarian follicle.
abstract: Vitellogenin (VTG) of Oreochromis niloticus was again purified, due to the conflicting results found in the literature. Three purification processes have been used: electrophoresis and electro-elution, double chromatography (gel filtration and ion-exchange chromatography) and single ion-exchange chromatography. Using SDS-PAGE we confirmed in all cases the presence of two polypeptidic forms of plasma VTG of 130 kDa (VTG1) and 170 kDa (VTG2). We raised polyclonal antibodies against each VTG form and we demonstrated the complete cross-reactivity of each antibody with both forms of VTG by Enzyme Immuno-Assay (EIA) and Western blots. The homologous ELISAs developed exhibited a detection limit of 6 ng x ml(-1), equivalent to 60 ng x ml(-1) of plasma VTG and allowed us to quantify the total plasma VTG of O. niloticus with high specificity and sensitivity. Using photonic and electron immunomicroscopy, we followed the pathway of VTG into the ovarian follicle (OF) demonstrating that VTG enters the oocyte at stage 3 of OF development, at the same time as cortical alveoli and lipid globules appear. Heterologous ELISAs performed on other cichlid species allowed us to quantify plasma VTG in Oreochromis aureus and Sarotherodon melanotheron and to detect it in Hemichromis fasciatus, Hemichromis bimaculatus and Tilapia zillii, constituting a reliable tool for monitoring the presence of xeno-estrogens in the environment of these fish species.
authors.affiliation: IFAN, Université Cheikh Anta Diop, Dakar, Sénégal.
authors.forename: Pap
authors.initials: P
authors.lastname: Ndiaye
authors.forename: Jean
authors.initials: J
authors.lastname: Forgue
authors.forename: Valérie
authors.initials: V
authors.lastname: Lamothe
authors.forename: Chantal
authors.initials: C
authors.lastname: Cauty
authors.forename: Philippe
authors.initials: P
authors.lastname: Tacon
authors.forename: Pierrette
authors.initials: P
authors.lastname: Lafon
authors.forename: Blandine
authors.initials: B
authors.lastname: Davail
authors.forename: Alexis
authors.initials: A
authors.lastname: Fostier
authors.forename: Françoise
authors.initials: F
authors.lastname: Le Menn
authors.forename: Jesús
authors.initials: J
authors.lastname: Núñez
mesh_terms: D000818:Animals; D023681:Cichlids / Q000378:metabolism*; D004586:Electrophoresis; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005260:Female; D029941:Fish Proteins / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism*; D005786:Gene Expression Regulation; D007120:Immunochemistry; D008297:Male; D006080:Ovarian Follicle / Q000378:metabolism* / Q000648:ultrastructure; D014819:Vitellogenins / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism*
chemical_list: D029941:Fish Proteins; D014819:Vitellogenins