Background and Objective

1. The impact of ovarian functions by ethylene glycol monomethyl ether extends across generation in female mice: a preliminary studyShao-Ping Weng, T.C. Jackson Wu, M.D., Ph.D., Pau-Chung Chen, M.D. Ph.D. Institute of Occupational Medicine and Industrial Hygiene, National Taiwan University College of Public HealthDivision of Reproductive Endocrinology and Infertility, David Geffen School of Medicine, UClLA Ethylene glycol monomethyl ether (EGME) has been found in various industrial and household products. Although EGME impacts reproductive functions of the exposed animals, its influence in the oocyte of offspring is not known. The aim of this study was to assess the toxicity of EGME on female offspring of exposed mice, ovulation rates as well as apoptosis of cumulus cells and oocytes from ovulation induction were examined. Background and Objective Conclusions • The litter size of F0 mice was not different among the four EGME dosage groups. The number of ovulated oocytes stimulated by PMSG and HCG was also similar between F0 and F1 mice among the four dosage groups. However, apoptosis rates (ARs) exhibited dose-dependent increases in the COCs of both F0 and F1 mice (Table). Furthermore, the ARs in COCs in F1 mice were 50-230% higher as compared to those of F0 mice. On the other hand, apoptosis in oocytes was only observed in the high dose groups in both F0 and F1 mice. Material and Methods Results Eight female ICR mice at six weeks of age were included in each of the four dosage groups, 0%, 0.05%, 0.1% and 0.2% of EGME. After one week of EGME exposure by means of gavage, four mice in each group were randomly selected and sacrificed to collect cumulus oocyte complexes (COCs) and oocytes for apoptosis tests using DAPI and TUNEL staining. The other four mice were cohabited with unexposed male mice to breed the F1 generation. When F1 female mice were at 6 weeks of age, the COCs and oocytes were collected following ovulation induction as described above for apoptosis tests. . 1. EGME exposure resulted in a significant and dose dependent increase in apoptosis of COCs in F1 mice, but a much less increase in apoptosis of oocytes. 2. The different reaction of EGME on COCs and oocytes suggests a protective role of cumulus cells on the enclosed oocyte. 3. The toxicity of EGME on ovarian functions may be due to the increased apoptosis of cumulus cells. 4. The adverse effects of EGME on reproductive functions seem able to pass to female offspring. However, conclusions will have to wait until experiments with large scale of animals can be conducted. Table 1. General data of EGME toxicity experiments. There are four parts in this table including pup numbers, retrieved oocyte numbers, apoptosis rates of cumulus-oocyte complexes (COCs) and apoptosis rates of oocytes. The apoptosis rates of COCs in F1 generation rise as the EGME doses increase. ns: not significant; n: positive TUNEL staining; N: total oocytes examined The values were presented as mean±SD. The p value at the last column, calculated by the Kruskal-Wallis test, represents the statistical significance among four groups. The statistical differences between control and study groups were compared by the Mann-Whitney test and the values were shown as follows: a<b, p=0.001 a<c, p=0.001 a<d, p=0.06 e<f, p=0.003 e<g, p=0.026 e<h, p<0.001 Corresponding author’s e-mail: pchen@ntu.edu.tw; First author’s e-mail: shaopingw@yahoo.com OMIH