Perinatal Toxicology: Its Recognition and Fundamentals

In vivo imaging of activated estrogen receptors in utero by estrogens and bisphenol A

Environmental estrogens are of particular concern when exposure occurs during embryonic development. Although there are good models to study estrogenic activity of chemicals in adult animals, developmental exposure is much more difficult to test. The weak estrogenic activity of the environmental estrogen bisphenol A (BPA) in embryos is controversial. We have recently generated transgenic mice that carry a reporter construct with estrogen-responsive elements coupled to luciferase. We show that, using this in vivo model in combination with the IVIS imaging system, activation of estrogen receptors (ERs) by maternally applied BPA and other estrogens can be detected in living embryos in utero. Eight hours after exposure to 1 mg/kg BPA, ER transactivation could be significantly induced in the embryos. This was more potent than would be estimated from in vitro assays, although its intrinsic activity is still lower than that of diethylstilbestrol and 17beta-estradiol dipropionate. On the basis of these results, we conclude that the estrogenic potency of BPA estimated using in vitro assays might underestimate its estrogenic potential in embryos.

Effects of in vitro cadmium exposure on ovarian steroidogenesis in rats

The purpose of this study was to evaluate the direct effect(s) of in vitro cadmium (Cd) exposure on steroidogenesis in rat ovaries during different reproductive states. Sprague-Dawley rats were killed on the day of proestrus, or on gestation day 6 or 16. Ovaries were removed, placed in medium and minced. Culture from each ovary was incubated with Cd2+ ions in concentrations of 0, 100, 500, 1000, 1500, or 2000 microM. One-hour whole-ovary production of progesterone (P4), testosterone and estradiol (E2) in culture medium was evaluated in the absence and presence of human chorionic gonadotropin (hCG) or hCG plus pregnenolone by specific radioimmunoassay. Under in vitro Cd exposure the most affected were productions of P4 and testosterone in proestrus rats and less in pregnant dams, whereas E2 was not affected at all. Cadmium appears to interfere with the ovarian steroidogenic pathway in rats at more than one site.

Occupational exposure and defects of the central nervous system in offspring: review

A study of published work was carried out in a search for evidence of a causal role for parental occupational exposure in the origin of structural and functional defects of the central nervous system (CNS) in children. Studies that consider this topic are scarce and mostly refer to broad categories of exposures and effects. Non-occupational studies referring to environmental exposure of humans and studies on experimental animals were also reviewed. The studies on animals provided straightforward evidence about morphological and behavioural abnormalities resulting from some agents used occupationally. The studies on humans yielded a scala of defects that could be ascribed to exposure to high doses of various agents in the environment. Evidence for a causal role of occupational exposure has not been found, but a highly probable influence on the developing CNS is hypothesised for lead, methyl mercury, and ionising radiation. Parental occupational exposure to cadmium, organic solvents, anaesthetics, and pesticides may also play a part in causing defects of the CNS. Well designed future research is needed to test the above hypotheses.

Teratogenic effects of methylnitrosourea on pregnant mice before implantation

Methylnitrosourea at a dose of 10 mg/kg is teratogenic when applied to pregnant mice on gestational days 2.5, 3.5 or 4.5, but has no such effects on gestational days 0.5 and 1.5.