Exposure to a Glyphosate-based Herbicide Alters the Expression of Key Regulators of Mammary Gland Development on Pre-pubertal Male Rats

Abstract

We previously reported that exposure during gestation and lactation to a low dose of glyphosate-based herbicide(GBH) reduced the area and perimeter of male offspring mammary gland at postnatal day 60 (PND60), whereas ahigher dose increased the longitudinal growth of the gland. Here, our aim was to assess whether perinatalexposure to GBH exhibits endocrine disruptive action in male mammary gland at an early time point (prepuberty),which could be related to the changes observed after puberty. We also wanted to explore whether anearly evaluation of the male rat mammary gland is appropriate to assess exposure to potential endocrine disruptingchemicals (EDCs). Pregnant rats were orally exposed, through the diet, to vehicle (saline solution), 3.5 or350 mg/kg/day of GBH from gestational day 9 until weaning. At PND21, the male offspring were euthanized,and mammary gland samples were collected. The histology and proliferation index of the mammary glands wereevaluated, and the mRNA expression of estrogen (ESR1) and androgen (AR) receptors, cyclin D1 (Ccnd1),amphiregulin (Areg), insulin-like growth factor 1 (IGF1), epidermal growth factor receptor (EGFR) and IGF1receptor (IGF1R) were assessed. Moreover, the phosphorylated-Erk1/2 (p-ERK1/2) protein expression was determined.No differences were observed in mammary epithelial structures and AR expression between experimentalgroups; however, the proliferation index was reduced in GBH3.5-exposed males. This result was associatedwith decreased ESR1, Ccnd1, Areg, IGF1, EGFR and IGF1R mRNA expressions, as well as reduced p-Erk1/2 protein expression in these animals. ESR1, Ccnd1, IGF1R and EGFR expressions were also reduced in GBH350-exposed males. In conclusion, the mammary gland development of pre-pubertal male rats is affected by perinatalexposure to GBH. Although further studies are still needed to understand the molecular mechanisms involved inGBH350 exposure, the present results may explain the alterations observed in mammary gland growth of postpubertalmales exposed to low doses of GBH. Our results also suggest that early evaluation of the male ratmammary gland is useful in assessing exposure to potential EDCs. However, analysis of EDCs effects at later timepoints should not be excluded.