Transcriptome of normal mammary glands of Sprague-Dawley rats at six stages of development: pre-pubertal, peri-pubertal, pubertal, lactation, adult parous and age-matched nulliparous

There is a lack of systematic investigations of large-scale transcriptome patterns associated with normal breast development. Herein, we profiled whole-transcriptome (by microarrays) of normal mammary glands in female Sprague-Dawley rats, an animal model widely used in breast cancer research, across six distinctive developmental stages – pre-pubertal, peri-pubertal, pubertal, lactation, and adult parous and age-matched nulliparous. Female Sprague-Dawley rats examined in this study are part of controls for a study on effects of environmental chemicals on developing mammary glands. These rats were regularly gavaged with olive oil by gastric intubation, the vehicle for chemical treatment in the parent study. Animals were sacrificed at six developmental time-points reflective of distinct stages of mammary gland development – pre-pubertal (n=10), peri-pubertal (n=5), pubertal (n=5), lactation (n=3), adult parous (n=5) and age-matched nulliparous (n=5). Pre-pubertal animals were sacrificed at postnatal day (PND) 21, peri-pubertal group at PND 42 and pubertal group at PND 63. Animals in the lactation group were sacrificed at the end of lactation at lactating day 28 (PND 146). Parous and age-matched nulliparous animals were sacrificed at PND 181.