Non-OECD mammalian screens and tests (Concptual Framework Levels 3-5)

Specific guidance is provided for in vivo screening assays validated at the national level by the US Environmental Protection Agency (the Pubertal Development and Thyroid Function Assay in Male Rats and the Pubertal Development and Thyroid Function Assay in Female Rats). These relatively short (31 days in the male, 21 days in the female) in vivo assays provide information on test chemical interaction with the sex steroid and thyroid hormone signalling pathways following administration of test chemical by oral gavage during the sensitive peri-pubertal period. Assay endpoints include the timing of reproductive advance (preputial separation or vaginal opening), organ weights, histopathology of reproductive and thyroid tissues, and thyroid hormone levels.