Carryover Effects of Acute DEHP Exposure on Ovarian Function and Oocyte Developmental Competence in Lactating Cows

Abstract

We examined acute exposure of Holstein cows to di(2-ethylhexyl) phthalate (DEHP) and its carryover effects on ovarian function and oocyte developmental competence. Synchronized cows were tube-fed with water or 100 mg/kg DEHP per day for 3 days. Blood, urine and milk samples were collected before, during and after DEHP exposure to examine its clearance pattern. Ovarian follicular dynamics was monitored through an entire estrous cycle by ultrasonographic scanning. Follicular fluids were aspirated from the preovulatory follicles on days 0 and 29 of the experiment and analyzed for phthalate metabolites and estradiol concentration. The aspirated follicular fluid was used as maturation medium for in-vitro embryo production. Findings revealed that DEHP impairs the pattern of follicular development, with a prominent effect on dominant follicles. The diameter and growth rate of the first- and second-wave dominant follicles were lower (P < 0.05) in the DEHP-treated group. Estradiol concentration in the follicular fluid was lower in the DEHP-treated group than in controls, and associated with a higher number of follicular pathologies (follicle diameter >25 mm). The pattern of growth and regression of the corpus luteum differed between groups, with a lower volume in the DEHP-treated group (P < 0.05). The follicular fluid aspirated from the DEHP-treated group, but not the controls, contained 23 nM mono(2-ethylhexyl) phthalate. Culturing of cumulus oocyte complexes in the follicular fluid aspirated from DEHP-treated cows reduced the proportion of oocytes progressing to the MII stage, and the proportions of 2- to 4-cell-stage embryos (P < 0.04) and 7-day blastocysts (P < 0.06). The results describe the risk associated with acute exposure to DEHP and its deleterious carryover effects on ovarian function, nuclear maturation and oocyte developmental competence.

Altered morphokinetics in equine embryos from oocytes exposed to DEHP during IVM

“…In this study, we used HS‐SPME coupled to GC–MS. While concentrations of DEHP metabolites have been reported in FF of women and cows (Du et al, ; Kalo et al, ; Krotz, Carson, Tomey, & Buster, ), to the best of our knowledge this is the first time that concentrations of DEHP itself have been measured in FF. This part of the study is of particular interest as the mare is a monovulatory species having translational relevance to human reproductive medicine (Alves et al, ; Bashir et al, ; Carnevale, ; Dell'Aquila et al, ).…”

“…Grossman, Kalo, Genderman, and Roth (), working in cattle, were the first to report effects of exposure of oocytes to DEHP on subsequent embryo development; oocyte exposure to 50 μM DEHP reduced the proportion of embryos developing to the blastocyst stage. The same group later reported that culturing cumulus‐oocyte complexes (COCs) in follicular fluid (FF) aspirated from cow follicles 25 days after the cows were treated with DEHP, and containing 23 nM MEHP (DEHP was not measured) reduced the rate of oocyte maturation to MII, the proportions of 2‐ to 4‐cell embryos, and the proportion of 7‐day blastocysts (Kalo et al, ). Investigations on the effects of DEHP and/or its metabolites on embryo development elicited by ovarian/oocyte exposure are still at their beginning, and at this time it is not clear whether DEHP directly influences early stages of embryo development.…”

Toxic Effects of Di-2-ethylhexyl Phthalate: An Overview

“…The antral follicle is an ovarian reserve and an important supplier of sex steroid hormones in females, and estradiol (E2) is necessary for follicle growth. DEHP affects follicle growth through a reduction of E2 levels in vitro [ 46 ]. A reduction of estradiol could decrease the expression of the Arom gene, which produces the aromatase enzyme, which converts testosterone to estradiol.…”

Stress‐induced alterations in oocyte transcripts are further expressed in the developing blastocyst

“…Similarly, in vitro culture of rat granulosa cells with 100 µM MEHP decreased estradiol production, most likely due to reduced expression of aromatase and alterations in the PPAR‐dependent signaling pathway (Lovekamp‐Swan & Davis ). Exposing cows to DEHP for 3 days induced alterations in the growth and development of the preovulatory follicle in the subsequent cycle, associated with reduced estradiol concentration in the follicular fluid (Kalo et al, ). In women, DEHP metabolites in the urine were associated with a reduced number of aspirated oocytes and of MII‐stage oocyte retrieval during the IVF cycle (Hauser et al, ).…”