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ARS Home » Research » Publications at this Location » Publication #31756
Title: CHANGES IN FOLLICULAR FLUID INSULIN-LIKE GROWTH FACTOR-BINDING PROTEIN-2 AND -3 DURING ATRESIA OF FOLLICLES GROWN AFTER OVULATION IN THE PIG

Author
item GUTHRIE H DAVID - 1265-10-00
item GRIMES R W - MS HERSHEY MED CENTER, PA
item HAMMOND J M - MS HERSHEY MED CENTER, PA

Submitted to: Journal of Reproduction and Fertility
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: Reproductive efficiency in the pig is heavily dependent upon the number and fertilizability of follicular oocytes. At any time during development, over 50% of ovarian follicles are undergoing atresia (an apoptotic form of programmed cell death) resulting in the death or abnormal development of their oocytes. Insulin-like growth factor (IGF) binding proteins (IGFBPs) antagonize the stimulatory effects of IGF-I on follicle cell differentiation and could play a role in follicular atresia. Reduction in the incidence of follicular atresia requires more knowledge about its causes and biochemical characteristics. DNA fluorescence flow cytometry was used to identify atretic follicles and measure apoptosis in follicle cells. The mean level of IGFBP-2 increased 3.3-fold between days 5 and 7 post-estrus. Levels of IGFBP-3 did not differ significantly among days. A subpopulation of follicle cells with degraded DNA was identified in follicles showing morphological signs of atresia and low levels of estroge production. We will use these results as a basis for studies on the molecular regulation of follicular growth and atresia in swine. These studies will provide knowledge required to better regulate ovulation rate.

Technical Abstract: This study was conducted to determine if changes in follicular fluid IGFBP levels in 3-6 mm, medium-size follicles were related to increased incidence of atresia. Individual follicles were isolated on days 5, 6, and 7 after the onset of estrus (day 0=first day of estrus) from eleven bred pigs. Follicles were identified as atretic by the presence of sub-diploid levels of DNA fluorescence in greater than 10% of their granulosa cells as determined by DNA fluorescence flow cytometry. IGFBP levels were determined by ligand blot analysis. The mean % apoptotic (Ao) cells/follicle increased from 3.6 to 35.0 and the mean level of IGFBP-2 increased 3.3-fold between days 5 and 7 post- estrus. Levels of IGFBP-3 did not differ significantly among days. Mean follicular fluid estradiol-17 concentration decreased from 52.3 to 0.9 ng/ml between days 5 and 7. Follicular fluid androstenedione also decreased between days 5 and 7, but progesterone did not differ significantly among days. IGFBP-2 was positively correlated wit %Ao cells (r=.898). IGFBP-2 was not significantly correlated with concentration of follicular fluid steroids or IGFBP-3. IGFBP-3 was correlated with follicle size (r=.397), but not with any other follicular variables. IGFBP-2 level was 3-fold greater in atretic than healthy follicles, but IGFBP-3 level did not differ significantly between atretic and healthy follicles. We conclude that increased production or accumulation of IGFBP-2 could play a role in the development of apoptosis among granulosa cells and increased follicular atresia between days 5 and 7 after estrus. In contrast, no physiological role for IGFBP-3 in apoptosis or atresia was indicated.