Estrogenicity relative estrogenic potency

In vivo studies in animals suggest that endosulfan may disrupt normal reproductive hormone levels in male animals, but that it is not an endocrine disrupter in females. Persistent depressed testicular testosterone was seen in male rats after intermediate duration oral exposures to endosulfan. In ovariectomized female rats, orally administered endosulfan did not induce normal development of female reproductive tissues, and in female mice and immature female rats, acute parenteral exposure to endosulfan did not affect several endocrine-related end points. In vitro studies have evaluated endosulfan for estrogen receptor (ER) and cytosolic protein binding affinity, ER-mediated reporter gene expression, estrogenic induction of cell proliferation, and alteration of relative abundance of active estradiol metabolites. Overall, in vitro evidence in favor of endosulfan estrogenicity indicates relatively weak potency compared to 17[3-estradiol. Apparently contradictory results were reported in different... 

Table 3 Relative estrogenic potencies as determined by different bioassays (expressed as EEF - the molar-based 17/5-estradiol equivalency factor) (adapted from [51])... 

In the Environment Canada distributional approach to characterise risks of NP, NPEO, and NPEC [8], relative toxicities were proposed based on categorising acute and chronic toxicities. A similar approach was used in that study to provide relative estrogenic potencies. Both are listed in Table 7.3.2 (Chapter 7.3). 

In Table 6 the physico-chemical properties, chemical structures, and some other relevant data of some natural estrogens, synthetic estrogens, and of some environmental man-made EDCs are compiled, as is the estrogenic activity measured as the relative proHferative potency on human breast cancer MCE 7 cells in the E-SCREEN assay [136] and in the recombinant yeast cell estrogen screening assay (RCBA) [138b]. In the last column of Table 6 their occurrence in the aquatic environment and their bioconcentration factors in fish and mussels are presented also as far as these data were pubHshed. 

Relative estrogenic potency compared to 17/i-estradiol (100) by molar mass determined with the recombinant yeast cell bioassay (RCBA) [138b]. Trade name. 

Relative Estrogenic Potency Determined by Yeast-based Assays... 

RELATIVE ESTROGENIC POTENCY DETERMINED BY YEAST-BASED ASSAYS... 

The relative estrogenic potency of a compound has been estimated by many different biological assays. Some values found in the literature are shown in Tables 5.3.1 and Table 5.3.2. The values are all given as Estradiol equivalency factors (EEF), defined as EC50 of the compound relative to the EC50 of 17ft-estradiol. 

Table 5.3.1 Relative Estrogenic Potency Of Selected estrogens...

Table 5.3.2 Relative Estrogenic Potency Of Selected Compounds...

Thorpe, K.L., Cummings, R.I., and Hutchinson, T. et al. (2003). Relative potencies and combination effects of steroidal estrogens in fish. Environmental Science and Technology 37, 1142-1149. 

Substance Aquatic toxicity Estrogenicity (relative potency to NP)a... 

Mixture toxicities. As is obvious from Chapters 2 and 6, APEO and their degradation products occur in the environment as complex mixtures. In risk characterisation studies of AP and APEO, the toxicity of individual constituents of such mixtures, whether assayed in acute and chronic toxicity, or in estrogenicity tests (Chapter 7), is being considered to occur, for each separate endpoint, through the same separate mode of action, and consequently to be additive. Thus, relative potencies can be established for each individual... 

Milligan SR, Balasubramanian AV, Kalita JC (1998) Relative potency of xenobiotic estrogens in an acute in vivo mammalian assay. Environ Health Perspect 106 23-26... 

Dichlorobenzenes can covalently bind to nucleic acids. In a concentration dependent manner, 1,2-dichlorobenzene and p-dichlorobenzene were found to be estrogenic in the yeast estrogen screen with relative potencies in relation to B-estradiol of 2.2 x 10 for 1,4-dichlorobenzene and 1.04x10 for 1,3-di-chlorobenzene. No mutagenic potential was observed in the gene mutation assay using mouse lymphoma cells. 

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