Neonatal exposure to endosulfan alters the uterine functional differentiation and impairs fertility in the rats

MILESI MM; GUERRERO SCHIMPF M.; INGARAMO P; ALARCÓN R; MUÑOZ-DE-TORO M; LUQUE EH; VARAYOUD J

Porto Alegre

Congreso; 1st Latin American Congress of Clinical and Laboratorial Toxicology.; 2014

Universidade Federal do Rio Grande do Sul

Introduction: Occupational and nutritional exposure to organochlorine pesticides has been associated with fertility disorders. Until recently, one of the most widely used organochlorine pesticides for agriculture purpose is endosulfan. Many experimental studies performed in rodents have associated early exposure to endosulfan during development with male reproductive toxicity; however, little is known regarding the effects on female reproductive performance. In the present study, we postulated that neonatal exposure to endosulfan impairs the female fertility affecting the implantation process. A successful implantation requires an intricate program of uterine preparation, where the glands and the integrity of the epithelium, as well as the expression of steroid receptors [progesterone receptor (PR) and estrogen receptor alpha (ERa)] play a crucial role. Objective: Investigate if a brief postnatal exposure to low doses of endosulfan affects the rat fertility and alters the uterine functional differentiation during pre-implantation period. Methods: Newborn female rats received vehicle (C) or endosulfan (600 ug/kg/day; END) on postnatal day 1, 3, 5, and 7. Then rats were pregnant (90 days old) and assigned to different studies: i) Fertility test: determining the pregnancy rate, the number of corpora lutea (CLs), and implantation and resorption sites at gestational day 19 (GD19); ii) Evaluation of uterine functional differentiation determining the gland number and luminal epithelial cell height (LECH) and molecular changes at protein (by immunohistochemistry) and mRNA (real-time RT-PCR) level, of PR and ERa at GD5 (pre-implantation period). Results: END-treated rats showed a decrease in the pregnancy rate (C: 100%; END: 77%) and in the number of implantation sites (C: 12±0.4; END: 9±1.0), without changes in the number of CLs and resorption sites (p<0.05). Endosulfan also induced morphological and molecular changes at GD5 in the uterine epithelium. END-treated rats showed an increase in the LECH (C: 16.5±0.5; END: 19.0±1.0, p<0.05), and a decrease in the number of glands (C: 43±0.5; E600: 29±1.0, p<0.05). At molecular level, an up regulation of ERa mRNA (C: 1±0.3; END: 1.8±0.5, p<0.05) was detected, without changes at protein level in the uterine epithelial cells. PR protein was up-regulated in both luminal and glandular epithelial cells (LE: C: 3.0±0.5; END: 6.0±1.0; GE: C: 2.5±0.3; END: 5.3±0.8, p<0.05). Conclusion: A postnatal exposure to low doses of endosulfan induced subfertility in female rats. We suggest that this effect is due -at least in part- to a modified uterine environment during the pre-implantation period since morphological and molecular alterations in the uterine tissue were found. Acknowledgments: This work was supported by grants from CONICET, ANPCyT and UNL.