Quantitative assessment of foetal exposure to trenbolone acetate, zeranol and melengestrol acetate, following maternal dosing in rabbits

1. Residues of commonly used growth-promoting agents found in animal meat can be hormonally active and they have been implicated as possible endocrine disruptors in man. Although these compounds could be potentially detrimental to the developing foetus, it is not clear whether and to what extent they pass through placental barrier. 2. This issue was addressed using the rabbit as an animal model. Pregnant rabbits were treated with trenbolone acetate, zeranol or melengestrol acetate beginning at gestation day 14. Levels of active substances in plasma were screened by means of specific ELISA systems. The residues of parent compounds and their metabolites were quantified in maternal and foetal tissues on gestation day 27 using validated, sensitive HPLC/ELISA methods. 3. All three compounds crossed the placental barrier and were detectable in foetal tissues. The extent of tissue concentration varied depending on the compound and tissue analysed. Gender differences were observed in some instances.