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ARS Home » Research » Publications at this Location » Publication #31755
Title: FOLLICULAR ATRESIA IN PIGS: MEASUREMENT AND PHYSIOLOGY

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

Submitted to: American Society of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/26/1995
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. Reduction in the incidence of follicular atresia requires more knowledge about causes and biochemical characteristics of follicular atresia. We used DNA fluorescence flow cytometry to develop a new technique to identify atretic follicles and measure apoptosis in follicle cells. A subpopulation of follicle cells with degraded DNA was identified in follicles showing morphological signs of atresia and low levels of estrogen 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: the physiological regulation of the atretic process in individual follicles was investigated by measuring DNA fluorescence in propidium iodide-stained Nuclei in ethanol-fixed granulosa cells by flow cytometry. Ovaries were recovered on days 1, 3, and 5 during altrenogest-synchronized preovulatory maturation and during the first wave of follicle growth on days 5, 6, and 7 7after the onset of estrus (day 0) in bred gilts. DNA cell cycle histograms revealed a subpopulation of apoptotic (Ao) granulosa cells of low fluorescence compared to cells in the Go/G1 peak. The %Ao granulosa cells/follicle ranged from 0.02 to 83.6. Follicles were classified as biochemically atretic (BA) or healthy (BH), respectively, if they contained > 10 or< 10% Ao granulosa cells. During preovulatory maturation only 5% of follicles >6 mm in diameter were BA. During preovulatory maturation atresia among medium-size follicles (3-6 mm) increased from 17 to 87% between days 1 and 5. Concentrations of estradiol (E2) and androstenedione (A4) were less in BA than in BH follicles. During the first wave of growth after ovulation, % BA follicles/pig increased from 6% on day 5 to 28% on day 6 and 50% on day 7. Follicular E2 was greater (P<.001) in BH than in BA follicles on days 5 and 6, but by day 7 E2 had decreased to a mean <1 ng/ml in both BH and BA follicles. Follicular A4 did not differ between BH and BA follicles, but decreased (P<.01) in both types between days 5 and 7. Follicular progesterone (P4) increased (P<.01) between days 5 and 7 in BA follicles and on day 7 was greater (P<.01) than in BH follicles. In conclusion, measurement of DNA content of granulosa cells identified atretic follicles that had increased apoptotic cell death and unique patterns of steroid production compared to healthy follicles in the pig.