Evaluation of a Tier I screening battery for detecting endocrine-active compounds (EACs) using the positive controls testosterone, coumestrol, progesterone, and RU486

After previously examining 12 compounds with known endocrine activities, we have now evaluated 4 additional compounds in a Tier I screening battery fo r detecting endocrine-active compounds (EACs): a weak estrogen receptor (ER ) agonist (coumestrol COUM), an androgen receptor (AR) agonist (testosteron e; TEST) a progesterone receptor (PR) agonist (progesterone; FROG), and a P R antagonist (mifepristone; RU486). The Tier I battery incorporates 2 short -term in vivo tests (5-day ovariectomized female battery; 15-day intact mal e battery) and an in vitro yeast transactivation system (YTS). The Tier I b attery is designed to identify compounds that have the potential to act as agonists or antagonists to the estrogen, androgen, progesterone, or dopamin e receptors; steroid biosynthesis inhibitors (aromatase, 5 alpha-reductase, and testosterone biosynthesis); or compounds that alter thyroid function. In addition to the Tier I battery, a 15-day dietary restriction experiment was performed using male rats to assess confounding due to treatment-relate d decreases in body weight. In the Tier I female battery, TEST administrati on increased uterine weight, uterine stromal cell proliferation, and altere d hormonal concentrations (increased serum testosterone [T] and prolactin [ PRL]; and decreased serum FSH and LH). In the male battery, TEST increased accessory sex gland weights, altered hormonal concentrations (increased ser um T, dihydrotestosterone [DHT], estradiol [E2], and PRL; decreased serum F SH and LH), and produced microscopic changes of the testis (Leydig cell atr ophy and spermatid retention), In the YTS, TEST activated gene transcriptio n in the yeast containing the AR or PR. In the female battery, COUM adminis tration increased uterine weight, uterine stromal cell proliferation, and u terine epithelial cell height, and increased serum PRL concentrations. In t he male battery, COUM altered hormonal concentrations (decreased serum T, D HT, E2; increased serum PRL) and, in the YTS, COUM activated gene transcrip tion in the yeast containing the ER. In the female battery, FROG administra tion increased uterine weight, uterine stromal cell proliferation, and uter ine epithelial cell height and altered hormonal concentrations (increased s erum progesterone and decreased serum FSH and LI-T). In the male battery, F ROG decreased epididymis and accessory sex gland weights, altered hormonal concentrations (decreased serum T, PRL, FSH, and LH; increased serum proges terone and E2), and produced microscopic changes of the testis (Leydig cell atrophy). In the YTS, FROG activated gene transcription in the yeast conta ining the AR or PR. In the female battery, RU486 administration increased u terine weight and decreased uterine stromal cell proliferation. In the male battery, RU486 decreased epididymis and accessory ses gland weights and in creased serum FSH and LH concentrations. In the YTS, RU486 activated gene t ranscription in the yeast containing the ER, AR, or PR. Dietary restriction data demonstrate that confounding due to decrements in body weight are not observed when body weight decrements are 10% or less in the Tier I male ba ttery. In addition, minimal confounding is observed at body decrements of 1 5% (relative liver weight, T-3, and T-4). Hence, compounds can be evaluated in this Tier I at levels that produce a 10% decrease in body weight withou t confounding of the selected endpoints. Using the responses obtained for a ll the endpoints in the Tier I battery, a distinct "fingerprint'' was produ ced for each type of endocrine activity against which compounds with unknow n activity can be compared. These data demonstrate that the described Tier I battery is useful for iden tifying EACs and they extend the compounds evaluated to 16.