Vitellogenin in tilapia (Oreochromis mossambicus): Induction of two forms by estradiol, quantification in plasma and characterization in oocyte extract

Abstract

Two forms of vitellogenin were isolated by DEAE agarose ion-exchange chromatography from plasma of the tilapia, Oreochromis mossambicus. The monomers have apparent molecular masses of 200 and 130 kDa, as indicated by SDS-polyacrylamide gel electrophoresis (SDS-PAGE), and a total amount of phosphorus of 1.7 and 0.1%, respectively. Antibodies specific to the two forms, designated tVTG-200 and tVTG-130, were generated in rabbits and used to develop enzyme-linked immunosorbent assays (ELISAs) and in Western blot analyses of plasma and oocyte extract. SDS-PAGE of the oocyte extract showed a major protein band at 106.6, minor bands at 26.6, 24.2, and 23.7 kDa, and very faint bands at 83.4 and 17.5 kDa. Western blots of the oocyte extract revealed that the antiserum to tVTG-200 recognized strongly the protein bands at 24.2 and 23.7 kDa, and less strongly the bands at 25.1 and 22.6 kDa, whereas the antiserum to tVTG-130 recognized mainly the protein band at 106.6 kDa. The presence of both VTGs in untreated male tilapia was detected with the ELISAs using relatively high plasma volumes. Their presence in males was confirmed by VTG-like immunoreactive materials eluting from the ion-exchange column at the same positions as tVTG-200 and tVTG-130. The concentrations of the VTGs in males were several orders of magnitude lower than in vitellogenic females. Treatment of male tilapia with estradiol-17β (E2) induced both VTGs within 24h. After 7 days, tVTG-130 reached a maximum concentration in plasma, whereas tVTG-200 continued to increase. Our findings demonstrate that the two vitellogenins are biochemically distinct, possibly differentially regulated, and made by both sexes.

Atlantic halibut (Hippoglossus hippoglossus) vitellogenin: induction, isolation and partial characterization

“…The presence of VTG in males has been reported previously in other fish species, such as the rainbow trout (Sumpter 1985) and has been at least partially ascribed to the presence of estrogen-like compounds, or phytoestrogens, in commercial fish diets (reviewed by Pelissero and Sumpter 1993). VTG, or VTG-like material, has also been detected in males of two species of tilapia, Oreochromus aureus (Ding et al 1989) and 0. mossambicus (Kishida and Specker 1994), which are plant-feeders and thus may ingest phytoestrogens as part of their natural diet. The halibut in the present study were fed a mixed diet of moist pellets and whole herring.…”

Vitellogenesis and choriogenesis in fishes

“…In contrast, because VtgC has a lower molecular weight than the other two types, it is relatively easy to purify. To date, the complete Vtg (VtgA and/or VtgB) and incomplete Vtg (VtgC) have been successfully isolated and purified as two different proteins with distinct molecular weights and antigenicity in various fish species, including tilapia (O. aureus [85] and O. mossambicus [86]), medaka [87], Japanese goby Acanthogobius flavimanus [88] and Sakhalin taimen [89]. In addition, three distinct types of Vtg have been purified or detected in mosquitofish Gambusia affinis [90], red seabream Pagrus major [91] and grey mullet [92].…”

Differential processing of yolk proteins during oocyte hydration in marine fishes (Labridae) that spawn benthic and pelagic eggs

“…It has been well documented that vitellogenin is the major source of yolk proteins in osteichthyan fishes (Ng & Idler 1983, Mommsen & Walsh 1988, Specker & Sullivan 1994, Johanning & Specker 1995, Tyler & Sumpter 1996, but only recently have multiple forms of vitellogenin been reported in teleosts. Multiple forms of vitellogenin, have been found in freshwater benthophils (Kishida & Specker 1993, Lee et al 1994, Trichet et al 2000, Wang et al 2000, in marine benthophils (LaFleur et al 1995), as well as in marine pelagophils (Matsubara et al 1999, Reith et al 2001. These latter studies have further mapped some of the oocyte proteins to the different vitellogenin cDNAs and argued that their hydrolysis was part of the mechanism that generates the FAA pool in pelagic fish eggs.…”