Mammary transcriptome of rats treated with low-dose environmental chemicals at critical developmental windows. Rattus norvegicus

Exposure to common environmental chemicals, including those found in personal care products has been linked to mammary cancer at high doses in animal models. Their effects at low doses at levels comparable to human exposure, especially during critical windows of development remain poorly understood. Using a Sprague-Dawley rat model, we investigated the effects of of three environmental chemicals – diethyl phthalate (DEP), methyl paraben (MPB) and triclosan (TCS) – on the transcriptome of normal developing mammary glands at low doses mimicking human exposure. Rats were exposed during three windows of early development – perinatal (gestation day (GD) 1 - 20 or postnatal day (PND) 1 - 20), prepubertal (PND 21 - 41) and pubertal (PND 42 - 62), as well as chronic exposure from birth to end of lactation (PND 1 - 146). Mammary gland whole-transcriptomes were profiled by Affymetrix rat gene 2.0 st arrays. Overall design: Female Sprague-Dawley rats were treated by oral gavage with low doses of diethyl phthalate (DEP), methyl paraben (MPB) or triclosan (TCS). These low doses were previously determined to produce urinary biomarker concentrations comparable to those reported for the US population (Teitelbaum SL et al, 2016). Control animals received the vehicle, olive oil (OIL). Exposure consisted of three short term windows – perinatal (gestation day (GD) 1 - 20 or postnatal day (PND) 1 - 20), prepubertal (PND 21 - 41) and pubertal (PND 42 - 62), as well as chronic exposure from birth to end of lactation (PND 1 - 146). There were 3-5 animals in each experimental group.