The Frog Embryo Teratogenesis Assay-Xenopus (FETAX) is a powerful and flexible bioassay that makes use of the embryos of the anuran amphibian Xenopus laevis. The FETAX can detect xenobiotics that affect embryonic development, when mortality, teratogenicity and growth inhibition are used as endpoints. The FETAX was used to compare the embryotoxic and teratogenic potentials of two chemical species of mercury: inorganic mercury(II) chloride (HgCl2) and organic methylmercury chloride (MeHgCl). MeHgCl, with an estimated median lethal concentration [LC50] of 0.313μM and a median teratogenic concentration [TC50] of 0.236μM, showed a higher toxicity than HgCl2, with estimated LC50 and TC50 values of 0.601μM and 0.513μM, respectively. On the basis of these results, HgCl2 and MeHgCl can be classified as “slightly teratogenic compounds”, as the ratio of LC50/TC50 is less than 1.5. There was a significant deviation from the commonly described monotonic behaviour of the concentration–response curves, suggesting a hormetic effect of both species of mercury. Uptake experiments, followed by neutron activation analysis, showed a higher incorporation of mercury in embryos exposed to MeHgCl compared with those exposed to HgCl2. Interestingly, Hg-exposed embryos showed a higher content of selenium and zinc than did control embryos.
SpielmannH. (1998). Reproduction and Development. Environmental Health Perspectives106, 571–576.
2.
BallsM., BlaauboerB.J., FentemJ., BrunerL., CombesR.D., EkwallB., FielderR.J., GuillouzoA., LewisR.W., LovellD.P., ReinhardtC.A., RepettoG., SladowskiD., SpielmannH., & ZuccoF. (1995). Practical aspects of the validation of toxicity tests procedures. The report and recommendations of ECVAM workshop 5. ATLA23, 129–143.
3.
BrownN.A., SpielmannH., BechterR., FlintO.P., FreemanS.J., JelinekR.J., KochE., NauH., NewallD.R., PalmerA.K., RenaultJ.Y., RepettoM.F., VogelR., & WigerR. (1995). Screening chemicals for reproductive toxicity: the current alternatives. The report and recommendations of ECVAM workshop 12. ATLA23, 868–882.
4.
DumontJ., SchultzT.W., BuchananM., & KaoG. (1983). Frog embryo teratogenesis Assay–Xenopus (FETAX): a short-term assay applicable to complex environmental mixtures. In Short-term Bioassays in the Analysis of Complex Environmental Mixtures (ed. WatersM.D., SandhuS.S., LewtasJ., ClaxtonL., ChernoffN., & NesnowS.), pp. 393–405. New York, NY, USA: Plenum Press.
5.
FortD.J., StoverE.L., BantleJ.A., RayburnJ.R., HullM., FinchR.A., BurtonD.T., TurleyS.D., DawsonD.A., LinderG., BuchwalterD., DumontJ.N., Kumsher-KingM., & Gaudet-HullA.M. (1998). Phase III interlaboratory study of FETAX. Part 2: interlaboratory validation of an exogenous metabolic activation system for frog embryo teratogenesis assay-Xenopus (FETAX). Drug and Chemical Toxicology21, 1–14.
6.
SundermanF.W.Jr, PlowmanM.C., & HopferS.M. (1991). Embryotoxicity and teratogenicity of cadmium chloride in Xenopus laevis, assayed by FETAX procedure. Journal of Clinical and Laboratory Science21, 381–391.
7.
SundermanF.W.Jr., PlowmanM.C., & HopferS.M. (1992). Teratogenicity of cadmium chloride in the South African frog, Xenopus laevis. In Cadmium in the Human Environment: Toxicity and Carcinogenity (ed. HerberR.F.M., & AlessioL.), pp. 249–256. Lyon, France: IARC.
8.
PlowmanM.C., Grbac-IvanovicS., MartinJ., HopferS.M., & SundermanF.W.Jr. (1994). Malformations persist after metamorphosis of Xenopus laevis tadpoles exposed to Ni2+, Co2+ or Cd2+ in FETAX assays. Teratogenesis, Carcinogenesis and Mutagenesis14, 135–144.
9.
KotyzovaD., & SundermanF.W.Jr. (1998). Maternal exposure to Cd(II) causes malformations of Xenopus laevis embryos. Journal of Clinical and Laboratory Science28, 224–235.
10.
PlowmanM.C., PerachaH., HopferS.M., & SundermanF.W.Jr. (1991). Teratogenicity of cobalt chloride in Xenopus laevis assayed by the FETAX procedure. Teratogenesis Carcinogenesis and Mutagenesis11, 83–92.
11.
SundermanF.W.Jr. (1992). Embryotoxicity and teratogenicity of Ni2+ and Co2+ in Xenopus laevis.Metal Compounds in Environment and Life (Interrelation between Chemistry and Biology)4, 467–474.
12.
LuoL.Q., PlowmanM.C., HopferS.M., & SundermanF.W.Jr. (1993). Embryotoxicity and teratogenicity of Cu2+ and Zn2+ for Xenopus laevis assayed by the FETAX procedure. Annals of Clinical and Laboratory Science23, 111–120.
13.
HopferS.M., PlowmanM.C., SweeneyK.R., BantleJ.A., & SundermanF.W.Jr. (1991). Teratogenicity of Ni2+ in Xenopus laevis assayed by the FETAX procedure. Biological Trace Element Research29, 203–216.
14.
SobotkaJ.M., & RahwanR.G. (1995). Teratogenesis induced by short- and long-term exposure of Xenopus laevis progeny to lead. Journal of Toxicology and Environmental Health44, 469–484.
15.
SundermanF.W.Jr., Grbac-IvankovicS., PlowmanM.C., & DavisM. (1996). Zn-2 + -induction of metallo-thionein in myotomal cell nuclei during somitogenesis of Xenopus laevis.Molecular Reproduction and Development43, 444–451.
16.
DeYoungD.J., BantleJ.A., & FortD.J. (1991). Assessment of the developmental toxicity of ascorbic acid, sodium selenate, coumarin, serotonin, and 13-cis-retinoic acid using FETAX. Drug and Chemical Toxicology14, 127–141.
17.
RayburnJ.R., DeYoungD.J., BantleJ.A., FortD.J., & McNewR. (1991). Altered developmental toxicity caused by three carrier solvents. Journal of Applied Toxicology11, 253–260.
18.
DomingoJ.L. (1994). Metal-induced developmental toxicity in mammals: a review. Journal of Toxicology and Environmental Health42, 123–141.
19.
BernardiniG., SpinelliO., PresuttiC., VismaraC., BolzacchiniE., OrlandiM., & SettimiR. (1996). Evaluation of the developmental toxicity of the pesticide MCPA and its contaminants phenol and chloro-cresol. Environmental Toxicology and Chemistry15, 754–760.
20.
SabbioniE., BallsM., PietraR., & FortanerS. (1999). The IMETOX project (In Vitro MEtal TOXicology). ATLA27, Special Issue, 107.
21.
BernardiniG., AndriettiF., CamantiniM., & CossonM.P. (1988). Xenopus spermatozoon: correlation between shape and motility. Gamete Research20, 165–175.
22.
NieuwkoopP.D., & FaberJ. (1967). Normal table of Xenopus laevis (Daudin).Amsterdam, The Netherlands: North-Holland.
23.
HausenP.H., & RiebesellM. (1991). The Early Development of Xenopus laevis: An Atlas of the Histology.Berlin, Germany: Springer.
BernardiniG., VismaraC., BoracchiP., & CamatiniM. (1994). Lethality, teratogenicity and growth inhibition of heptanol in Xenopus assayed by a modified FETAX procedure. Science of the Total Environment151, 1–8.
26.
SabbioniE., PietraR., SerraM.A., FortanerS., EdelJ., & MinoiaC. (1993). Application of nuclear, radiochemical and spectrochemical techniques in metal toxicology. Journal of Trace Microprobe Techniques11, 217–233.
27.
BreslowN.E., & ClaytonD.G. (1993). Approximate inference in generalized linear models. Journal of the American Statistical Association88, 9–25.
28.
FinneyD.J. (1971). Probit Analysis, 3rd Edition.Cambridge, UK: Cambridge University Press.
29.
KhuriA.I., MathewT., & SinhaB.K. (1998). Statistical Tests for Mixed Linear Models.New York, NY, USA: John Wiley & Sons.
30.
ClarksonT.W. (1992). Mercury: major issues in environmental health. Environmental Health Perspectives100, 31–38.
31.
WoodJ.M., KennedyF.S., & RosenC.E. (1969). Synthesis of methylmercury compounds by extracts of methanogenic bacteria. Nature, London220, 173–174.
32.
LindqvistO., JohanssonK., AastrupM., AnderssonA., BringmarkL., HovseniusG., HakansonL., IverfeldtA., MeiliM., & TimmB. (1991). Mercury in the Swedish Environment: recent research on causes, consequences and corrective methods. Water, Air, Soil Pollution55, XI–XIII.
33.
ShimaiS., & SatohH. (1985). Behavioral teratology of methylmercury. Journal of Toxicological Science10, 199–216.
34.
HaradaJ. (1995). Minamata disease: methylmercury poisoning in Japan caused by environmental pollution. Critical Reviews in Toxicology25, 1–24.
35.
World Health Organization (1990). Environmental Health Criteria 101. Methylmercury p. 102.
36.
RepettoG., SanzP., & RepettoM. (1993). In vitro effects of mercuric chloride and methylmercury chloride on neuroblastoma cells. Toxicology in Vitro7, 353–357.
37.
BerlinM. (1986). Handbook on the Toxicology of Metals. pp. 386–445. Amsterdam, The Netherlands: Elsevier Scientific Publishing.
38.
MehraR.H., BawaS.R., & KanwarK.G. (1980). 203Hg binding in the liver and kidney of the frog Rana tigrina.Toxicology Letters6, 37–41.
39.
KostaL., ByrneA.R., & ZelenkoV. (1975). Correlation between selenium and mercury in man following exposure to inorganic mercury. Nature, London254, 238–239.
40.
MagosL., & WebbM. (1976). The interaction between cadmium, mercury and zinc administered subcutaneously in a single injection. Archives of Toxicology36, 53–61.
41.
CalabreseE.J. (1999). Evidence that hormesis represent an overcompensation response to a disruption in homeostasis. Ecotoxicological and Environment Safety42, 135–137.
42.
CraggB., & ReesS. (1984). Increased body–brain weight ratio of developing rats after low exposure to organic lead. Experimental Neurology86, 113–121.
43.
GantherH.E. (1979). Modification of methylmercury toxicity and metabolism by selenium and vitamin E: possible mechanisms. Environmental Health Perspectives25, 71–76.
44.
SabbioniE., & MarafanteE. (1975). Heavy metals in rat liver cadmium binding protein. Environmental Physiology and Biochemistry5, 132–141.
45.
GaleT.F., & FermV.H. (1971). Embryopathic effects of mercury salts. Life Sciences10, 1341–1347.
BantleJ.A., FinchR.A., FortD.J., StoverE.L., HullM., Kumsher-KingM., & Gaudet-HullA.M. (1999). Phase III interlaboratory study of FETAX. Part 3: FETAX validation using 12 compounds with and without an exogenous metabolic activation system. Journal of Applied Toxicology.19, 447–72.
48.
FortD.J., StoverE.L., FarmerD.R., & LemenJ.K. (2000). Assessing the predictive validity of frog embryo teratogenesis assay-Xenopus (FETAX). Teratogenesis, Carcinogenesis and Mutagenesis20, 87–98.
