Intrauterine and lactational exposure of male rats to supraphysiological doses of manganese: reproductive, renal and hepatic toxicity

Abstract

Manganese (Mn) is the second most abundant element in the environment, being less prevalent only than iron. It occurs naturally in the air, water, soil and food. Mn deficiency in animals and humans can result in growth retardation, poor bone formation, reduced fertility, birth defects, among others. On the other hand, exposure to high levels of manganese, which can occurs through agricultural fungicides, atmospheric emissions, drainage and spills, is related to diseases such as inflammation of lungs, acute renal dysfunction, and impairment of neurological/psychological functions. Regarding the reproductive system, accumulation of Mn can cause morphometric changes in the organs and impair spermatogenesis, impacting the fertile ability of the animals. Despite the relevance of the fetal/perinatal period for toxicological studies on Mn, data available in the literature deal only with the physical and neurological development of the offspring. There are no studies evaluating animals exposed to Mn during intrauterine and lactational life regarding their reproductive health during postnatal development. Considering that previous study from our laboratory has indicated that Sertoli cells may be an important target of Mn toxicity in adult rats, the present study aims to investigate whether gestational and lactational exposure (period of Sertoli cell formation and proliferation) to Mn will compromise reproductive function of male offspring. For this, in vivo study will be performed with pregnant Wistar rats randomly distributed into 3 experimental groups (n=10/group: control, receiving only water via gavage; Mn1, low dose, will receive MnCl2 via gavage at dose to be defined in study of acute toxicity; Mn2, high dose, will receive MnCl2 via gavage, at dose to be defined in study of acute toxicity). Pregnant/nursing mothers will receive the experimental treatment from gestational day 13 until lactational day 15 (post natal day-PND 15 of the pups). At PND 15, 50 or 90, one male of each litter (totaling n=10/group/age) will be submitted to euthanasia for evaluation of reproductive, hepatic and renal parameters. In parallel, in vitro study with Sertoli cells of the TM4 lineage will be conducted to investigate the direct effects of Mn on cytotoxicity, cell morphology, and biomarkers of proliferation, apoptosis, maturity and methylation of Sertoli cells. (AU)