New methods for detection of potential endocrine disruptors.

It has been hypothesized that recent adverse trends in humans are linked to an increased exposure to potential endocrine disrupting agents. These include widely used compounds that mimic the action of sex hormones, including bisphenol A, phthalates and parabens. Since the chemical structure is not sufficient to determine whether a chemical will act as an oestrogen, there is a need for assays that can determine whether a compound interferes with the endocrine systems. The Environmental Protection Agency has recently suggested a testing scheme, composed of an initial screening followed by a more comprehensive investigation of chemicals that are positive in the screening. The screening will use several short-term assays to screen many thousands of compounds for potential endocrine disrupting properties. However, none of these tests determines compound-induced effects on the expression of endogenous genes, which is the cause of the adverse effects. We propose to use a precise quantification of the expression levels of endogenous oestrogen-regulated genes to test whether a chemical has oestrogenic properties, and describe how an endogenous gene expression assay can be established and conducted. Furthermore, different applications of such an assay are discussed: in cell cultures; in experimental animals; or, optimally, directly in blood samples from exposed humans.

A dose-finding study of in utero and lactational exposure to diethylstilboestrol and flutamide in 129/Sv mice.

The purpose of the study was to test the experimental conditions and find the appropriate dose range for further investigations of the disruptive effects of oestrogens and antiandrogens on the development of testis. Groups of four 129/Sv mice were exposed from day 6 after mating until weaning to 1, 10 or 100 microg/kg/day of the non-steroidal oestrogen diethylstilboestrol and to 0.1, 1 or 10 mg/kg/day of the non-steroidal antiandrogen flutamide. The number of implantation sites, the litter size and reproductive parameters were examined and nipple development, anogenital distance and testicular morphology were investigated in the offspring. Dose-related post-implantation loss was seen in both diethylstilboestrol- and flutamide-treated dams and the mean litter size was smaller in the groups given the high dosages of diethylstilboestrol and flutamide. Disturbance of testicular development was seen in males exposed to diethylstilboestrol. Because of the small data material, no statistical analyses were performed. Our findings indicate that very high doses of both diethylstilboestrol and flutamide given at early stages of gestation result in a high post-implantation loss and should be avoided in further experiments using this strain which is known to have a poor reproductive performance. Exposure of the dams before mating may better reflect human exposure, but will presumably require even lower dose levels.