Ovary

Effect of Maternal Exposure to the Environmental Estrogen, Octylphenol, During Fetal and/or Postnatal Life on Onset of Puberty, Endocrine Status, and Ovarian Follicular Dynamics in Ewe Lambs

Abstract

Octylphenol (OP) is one of a number of compounds found in the environment that has estrogen mimicking actions in vivo. Our objective was to determine if maternal exposure to octylphenol during fetal and/or postnatal life would affect the onset of puberty, endocrine status and subsequent ovarian follicular dynamics of ewe lambs. Lambs were born in March to ewes that received twice weekly subcutaneous injections of octylphenol (1000µg/kg/day) from day 70 of gestation to weaning (n=6); day 70 of gestation to birth (n=3); birth to weaning (n=5; gestation = 145 days) or corn oil from day 70 of gestation to weaning (control; n=5). Blood samples were collected twice weekly to determine progesterone and FSH concentrations from 20 weeks of age throughout the first breeding season. Onset of puberty and interestrous intervals were determined from 20 weeks of age by twice daily observation for estrus in the presence of a vasectomized ram. During January the ovaries of each lamb were examined using transrectal ultrasonography from the day of estrus for 15 days. Blood samples were collected every 8 hours to examine FSH concentrations and every 2 hours to detect the pre-ovulatory gonadotropin surge throughout this estrous cycle. The onset of puberty and first progesterone rise was advanced and the FSH pre-ovulatory surge was elevated for longer in the OP-treated lambs compared to the control lambs (p<0.05). Interestrous intervals, FSH profiles and ovarian follicular dynamics were not affected (p>0.05) by exposure to octylphenol. In conclusion, octylphenol exposure advanced the onset of puberty but it did not disrupt FSH concentrations or the dynamics of ovarian follicular growth.