Vitellogenin endocrine disruption

Measurement of contaminants in fish has concentrated on muscle tissue since the aim has generally been to protect the health of the consumer rather than that of the fish. Endocrine tissue such as the gonads has been much more rarely examined, while data for adrenal, thyroid and pituitary levels are virtually non-existent. More data are available for the liver, as a lipid rich tissue and the major site of xenobiotic catabolism, but the concentrations have rarely been related to its capacity to produce vitellogenin or metabolise endogenous hormones. Tissue concentrations of a wide range of chemicals, are at a level which suggests that, either alone or in combination, they will cause significant endocrine disruption in fish in many polluted habitats. 

The liver plays an important role in the endocrine system. The concentrations of hormones in plasma, and the activity of the glands which secrete them, are determined by the rate at which they are deactivated by the liver. The liver also has a major function in female reproduction since it is the target tissue of ovarian estrogen, to which it responds by producing the yolk protein vitellogenin. " Xenobiotics that affect either of these functions can therefore be considered to be potential endocrine disrupters. 

There is some evidence for chemically mediated endocrine disruption in amphibians. The egg yolk protein, vitellogenin, is inducible in amphibians by exposure to DDT. " Males of the short clawed toad Xenopus laevis given 250 fig/g or 1 fig/g o,p -DDT for seven days have been shown to produce vitellogenin, although the induction was less than that achieved by treatment with 1 fig/g of either 17/1-oestradiol or diethylstilboestrol. Research has also shown that endocrine disrupting chemicals can alter sex ratios in wild populations of certain species PCB congeners and organochlorine compounds have been linked with male domination of sex ratios in polluted compared to unpolluted sites. ... 

Garcia-Reyero N, Raldua D, Quiros L, Llaveria G, Cerda J, Barcelo D, Grimalt JO, Pina B (2004) Use of vitellogenin mRNA as a biomarker for endocrine disruption in feral and cultured fish. Anal Bioanal Chem 378 670-675... 

Petty et al. (1998, 2000) used a vitellogenin (VGT) assay to assess the endocrine disrupting potential of contaminants in purified SPMD extracts. VGT is an egg yolk phosphoprotein precursor that is synthesized in the liver of female teleosts in response to estrogen from the ovary (Bailey, 1957). A wide variety of environmental contaminants have been shown to have estrogenic activity (Colborn et al., 1993). Equal portions of purified extracts from SPMDs, exposed in the Missouri River after the flood of 1993 and from the IWWTP at the Nogales Wash deployment were individually injected into immature rainbow trout (Oncorhynchus mykiss) as described in Section 6.4. The SPMD extracts contained elevated levels of complex mixtures of contaminants, including PAHs and pesticides. The fish injected with these sample extracts exhibited VGT induction, while no induction was observed in fish injected with any of the blank sample extracts. 

Kirby, M.F., Allen, Y.T., Dyer, R.A., Feist, S.W., Katsiadiki, I., Matthiessen, P., Scott, A.P., Smith, A., Stentiford, G.D., Thain, J.E., Thomas, K.V., ToUiurst, L., Waldock, M.J. (2004). Surveys of plasma vitellogenin and intersex in male flounder (Platichthys flesus) as measures of endocrine disruption by estrogenic contamination in United Kingdom estuaries temporal trends, 1996 to 2001. Environmental Toxicology and Chemistry, 23 748-758. 

An important question in this area relates to the widespread use of exposure biomarker responses for monitoring effluents and receiving waters for endocrine disrupter activity. In oviparous species, vitellogenin is the major example of such a... 

John R Giesy, Shane Snyder and coworkers from the Institute of Environmental Toxicology at Michigan State University studied effluents from several different types of municipal waste water treatment plants in central Michigan. They also came to the conclusion that human hormones (17 -estra-diol) and synthetic hormones (ethinylestradiol), not industrial chemicals with estrogenic activity, in the efQuents caused male fish to produce vitellogenin, a well-accepted indicator of endocrine disruption [145d]. 

Reproduction To assess reproductive status. Alteration of reproduction could have more direct impacts on population status Decreased vitellogenesis in females or increased vitellogenin levels in males (endocrine disruption)... 

Blaise, C., Gagne, F., Pellerin, J. and Hansen, P.-D. (1999) Determination of vitellogenin-like properties in Mya arenaria hemolymph (Saguenay Fjord, Canada) a potential biomarker for endocrine disruption. Environ. Toxicol., 14, 455-465. 

Fossi, M.C., S. Casini, S. Ancora, A. Moscatelli, A. Ausili and G. Notarbartolo-di-Sciara. Do endocrine disrupting chemicals threaten Mediterranean swordfish Preliminary results of vitellogenin and zona radiata proteins in Xiphias gladius. Mar. Environ. Res. 52 447-483, 2001. 

From these studies, some patterns of effect potentially mediated by the endocrine system have been observed. These include the accumulation of vitellogenin in ticks [50-52] and accelerated ovarian development in beetles and ticks [51, 53]. Different researchers have attributed these effects to a range of different mechanisms, including induced excitation of neurosecretory cells releasing juvenile hormone [50], and ecdysteroid disruption either by blocking the neuropeptide itself or at the epidermal site of synthesis [51]. Other researchers have not corroborated these results and have even found contradictory effects, e.g., suppressed ovarian development [52], Therefore at present for SPs, there is no clear evidence for adverse population-relevant effects with an underlying endocrine mode of action. 

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