Inoviparousanimals,vitellogenin(VTG)isanestrogen-inducedyolkprecursorproteinmainlysynthesizedinthelivertobedepositedinthematuringoocytes,whereitissplitintheyolkproteinslipovitellin1,lipovitellin2andphosvitin.Theseyolkproteinsserveasnourishmentstorageforthedevelopingembryos.Non-physiologicalinductionofvitellogenininmalesorinjuvenilefishisthoughttoindicateanestrogenmediatedendocrinedisruption.ThereforeVTGdeterminationisoneofthecoreendpointsinscreeningandtestingforendocrinedisruptingchemicalsstandardizedintheOECDGuidelinesforthetestingofchemicalsforestrogenicactivity.Normally,vitellogeninismeasuredinbloodsamplesorwholebodyhomogenate(WBH)–bothsampletypesrequireinvasiveanddestructivetreatmentofthefish.Bloodcanbe difficulttocollect,inparticularwhereverysmallfishareconcernedand wheretheanimalsmustsurvivesampling.

Recently,severalcelltypeshavebeenshowntoproduceVTGafterestrogenstimulation,includingthoseoftheepidermalmucosa.EventhoughtheVTGconcentrationintheskinmucusisanorderofmagnitudelowerthaninbloodserumorinbodyhomogenates(containinglivertissue),theskinmucosaisverywellsuitedasamatrixfor determiningexogenousVTGinductioncausedbyenvironmentalchemicalswithaffinitytoestrogenreceptors.ByusingahighlysensitiveELISAincombinationwithauniquesamplingandextractionsystemthedeterminationofmucosa-bornVTGdeterminationhasthefollowingadvantages:

  • Simpleandhighlystandardizedsamplingtechniqueandsamplepreparation.
  • Strictlydefinedmatrixwithoutproteasecontaminationcausedbynon-targettissuesorlymphaticfluid.
  • Non-destructiveandtherebyallowingseveralsubsequentsamplingsinordertorecordakineticofVTGinductionwithamaximumknowntoappearafter7daysofexposure.ThereforMucosatestarefullycompatIBLewithacuteaswellaschronicalOECDtestmethods.
  • Epithelialorganizedepidermisisdirectlyexposedtoexogenousestrogensandtherebyallowingadirectcomparisonwithinvitrotestusingestrogensensitivevitellogeninproducingfishcelllines.
  • LowerdegreeofinterferencewithendogenousVTGproduction(infemales)andbioconcentrationorenterohepaticcirculationoftheeffectiveestrogen(xenoestrogen)andtherebyshowingacleardoseresponserelationship.
  • StABIlityofstandardsandsamplesifprescribedstorageconditionsareobserved.

TheTECO®REACHCyprinidVitellogeninELISAkitallowsforsamplingofblood,homogenateand/ormucuswhichprovides researcherswithsampling optionswhen conductingtime-coursestudiesorfieldresearchwhereitiscriticaltopreservethelifeofthefish.