title: Inter-laboratory comparison of a yeast bioassay for the determination of estrogenic activity in biological samples.
abstract: An inter-laboratory exercise was performed with a yeast estrogen bioassay, based on the expression of yeast enhanced green fluorescent protein (yEGFP), for the determination of estrogenic activity in extracts of calf urine samples. Urine samples were spiked with 1 and 5 ngmL(-1) 17beta-estradiol and 17alpha-ethynylestradiol, 10 and 50 ngmL(-1) mestranol, and 100 ngmL(-1) testosterone and progesterone. Sample extracts of blank and spiked urine samples were prepared at our laboratory and sent to seven laboratories together with a reagent blank, a DMSO blank, and eight 17beta-estradiol stock solutions in DMSO ranging in concentration from 0 to 545 ngmL(-1). Sample extracts and standards were coded and tested blindly. A decision limit (CCalpha) was determined based on the response of seven blank urine samples. Signals of the negative controls, e.g. urine samples spiked with 100 ngmL(-1) testosterone or progesterone, were all below the determined CCalpha and were thus screened as compliant. Positive controls, i.e. the urine samples spiked at two levels with 17beta-estradiol, 17alpha-ethynylestradiol and mestranol, were almost all screened as suspect, i.e. gave signals above the determined CCalpha. Determined EC(50) values calculated from the 17beta-estradiol dose-response curves obtained by the seven laboratories ranged from 0.59 to 0.95 nM.
authors.affiliation: RIKILT-Institute of Food Safety, Wageningen University and Research Centre, P.O. Box 230, 6700 AE Wageningen, The Netherlands.
authors.forename: Toine F H
authors.initials: TF
authors.lastname: Bovee
authors.forename: Gerrit
authors.initials: G
authors.lastname: Bor
authors.forename: Ilse
authors.initials: I
authors.lastname: Becue
authors.forename: Frieda E J
authors.initials: FE
authors.lastname: Daamen
authors.forename: Majorie B M
authors.initials: MB
authors.lastname: van Duursen
authors.forename: Sylvi
authors.initials: S
authors.lastname: Lehmann
authors.forename: Günter
authors.initials: G
authors.lastname: Vollmer
authors.forename: Raffaella
authors.initials: R
authors.lastname: De Maria
authors.forename: Jennifer E
authors.initials: JE
authors.lastname: Fox
authors.forename: Hilda
authors.initials: H
authors.lastname: Witters
authors.forename: Silke
authors.initials: S
authors.lastname: Bernhöft
authors.forename: Karl-Werner
authors.initials: KW
authors.lastname: Schramm
authors.forename: Ron L A P
authors.initials: RL
authors.lastname: Hoogenboom
authors.forename: Michel W F
authors.initials: MW
authors.lastname: Nielen
mesh_terms: D000818:Animals; D001681:Biological Assay / Q000379:methods* / Q000592:standards; D002417:Cattle; D019411:Clinical Laboratory Techniques; D004967:Estrogens / Q000737:chemistry / Q000302:isolation & purification / Q000652:urine*; D049452:Green Fluorescent Proteins / Q000737:chemistry; D049408:Luminescent Agents / Q000737:chemistry; D015003:Yeasts / Q000378:metabolism*
chemical_list: D004967:Estrogens; D049408:Luminescent Agents; D049452:Green Fluorescent Proteins