Collaborative work on evaluation of ovarian toxicity 10) Two- or four-week repeated dose studies and fertility study of di-(2-ethylhexyl) phthalate (DEHP) in female rats

Abstract

INTRODUCTIONAs part of a collaborative study on toxicity related to female fertility, we performed experiments using di-(2-ethylhexyl) phthalate (DEHP), widely used as a plasticizer of polyvinyl chloride (PVC) and a known peroxisome proliferator (Lake et al., 1987), liver carcinogen (Reddy and Lalwai, 1983) and ovarian toxicant in rodents (Davis et al., 1994). Short-term exposure to DEHP resulted in hypoestrogenic anovulatory cycles and polycystic ovaries in adult rats (Davis et al., 1994). Longterm exposure to DEHP resulted in continuous diestrous stage with reduced serum estradiol, follicle stimulating hormone (FSH), pituitary FSH and luteinizing hormone (LH) (Hirosawa et al., 2006). The active metabolite of DEHP mono-(2-ethylhexyl) phthalate (MEHP) decreased aromatase in rat granulosa cells in vitro (Davis et al., 1994). Because the toxic effects of DEHP on ovaries are thought to be endocrine disorders and an aromatase inhibitor is expected to impact both ovarian morphology and female fertility, we selected DEHP as the test compound for the evaluation of ovarian toxicity.The present study was designed to determine whether 2-or 4-week administration periods for detecting histopathological changes in a repeated-dose toxicity study to compare the potential ovarian toxicity with the female reproductive function in a fertility study. MATERIALS AND METHODS Test articleDEHP was obtained from Kanto Chemical (Tokyo, Japan). Corn oil was purchased from Sigma-Aldrich Japan (Tokyo, Japan) and used as a vehicle. DEHP was ABSTRACT -The main purpose of this collaborative work is to determine the optimal administration period required to detect toxic effects in evaluation of ovarian morphological changes in repeated-dose toxicity studies. To assess the morphological and functional changes induced in the ovaries by di-(2-ethylhexyl) phthalate (DEHP), two repeated-dose toxicity studies (repeated dose for 2 or 4 weeks) of DEHP administrated to female rats at dose levels of 0, 300, 1,000 and 3,000 mg/kg were conducted in collaboration with a female fertility study at the same dosages from 2 weeks prior to mating to Day 7 of pregnancy. Histopathology of the ovaries in both repeated-dose toxicity studies showed vacuolation of stromal cells in the groups receiving 300 mg/kg or more and an increase of large atretic follicles in groups at 1,000 mg/ kg or more. In the 4-week study, a decrease in new corpora lutea was observed in the 3,000 mg/kg group. In the female fertility study, the 3,000 mg/kg group showed prolongation of the mean estrous cycle and irregular estrous cycles. Cesarean section revealed a decrease of pregnancy rate in the 3,000 mg/kg group. No effects on fertility or early embryonic development were found in groups at 1,000 mg/kg or less. -ation of drugs which induce ovarian damage. In conclusion, for a repeated-dose toxicity study, a 2-week

Prenatal exposure to di-(2-ethylhexyl) phthalate (DEHP) affects reproductive outcomes in female mice

“…These studies have observed effects of DEHP exposure such as reduced anogenital distance, reduced testes weights, reduced testosterone production [17, 25], delayed pubertal onset, and abnormal seminiferous tubule formation [26]. A few studies have examined the effects of exposure to DEHP on female reproduction [28, 33-35]. These studies have shown that DEHP exposure causes a decline in pregnancy rates and irregular estrous cyclicities at very high doses [33], decreased overall fertility [34], atresia of tertiary follicles in adult rats, and delayed onset of puberty [35].…”

The influence of antenatal exposure to phthalates on subsequent female reproductive development in adolescence: a pilot study

“…Consequently, it is virtually impossible to avoid chronic low-level exposure to phthalates. It is of note that MEHP, a metabolite of DEHP, which has been reported to lead to oocyte atresia (Takai et al 2009), suppresses oestradiol (E 2 ) synthesis and ovulation in female rats. In addition, MEHP leads to a reduced size of pre-ovulatory follicles and suppresses follicular development when cultured in vitro .…”

Effects of DEHP on endometrial receptivity and embryo implantation in pregnant mice

“…Females with chronic and long-term exposure to high levels of DEHP are especially prone to negative reproductive outcomes, i.e., low pregnancy and high miscarriage rates [9,10], irregular estrogen and progesterone levels with no ovulation [11,12], and pregnancy complications such as anemia, hypertensive disorders and pre-eclampsia [13]. Although DEHP apparently compromises pregnancy outcomes in female, the underlying mechanism is still unclear.…”