Longitudinal Changes in Ovarian Function with Aging in Sprague Dawley Rats

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: MON 515-547-Female Reproductive Endocrinology
Monday, June 17, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board MON-537
Janet L Funk*1, Ashley L Lukefahr2 and Jen B Frye1
1University of Arizona, Tucson, AZ, 2University of Arizona, Phoenix, AZ
Ovariectomized (OVX) rats are frequently used to model human menopause.  When comparing outcomes in OVX vs. age-matched controls, the reproductive state of the control rats must also be considered.  Experiments were thus undertaken to characterize age-related changes in ovarian function, as determined by vaginal cytology, and ovarian hormone production, as determined by assay of serum hormones, in female Sprague Dawley rats beginning at 1 month of age and ending at 20 months of age.  Rats began to enter an acyclic stage of persistent estrus at 7 months of age that peaked in incidence at 12 months and persisted until the final cyclicity screen at 18 months of age; 17-beta estradiol (E2) levels remained essentially unchanged throughout this period.  Serum inhibin A and FSH levels began to increase at 5 months prior to the onset of persistent estrus, peaking at 12 months and remaining elevated until 20 months.  Inhibin B levels declined throughout this period.  Serum FSH and E2 at 20 months were 3–fold lower and 2-fold higher, respectively, than age-matched rats that had been subjected to OVX 5 months earlier.  BMD of the distal femur, which plateaued by 5 months of age, declined by 16% relative to age-matched controls in OVX rats at 20 months.  In conclusion, while acyclic aging rats remain estrogen replete until 20 months of age due to the onset of persistent estrus, other significant hormonal changes accompany ovarian senescence beginning at 5 months of age, most notably increases in FSH and inhibin A.  Interestingly, and consistent with previous reports, OVX of aged rats resulted in an even greater increase in FSH levels, while only decreasing E2 levels by half.  Thus, aged female Sprague Dawley rats, with or without OVX, were less estrogen-deficient than women undergoing the menopausal transition.

Nothing to Disclose: JLF, ALL, JBF

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

Sources of Research Support: NIH grant R21AT003614 to JLF