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Title: INSULIN-LIKE GROWTH FACTOR-BINDING PROTEINS-2 AND -3 ARE CORRELATED WITH ATRESIA AND PREOVULATORY MATURATION IN THE PORCINE OVARY

Author
item GRIMES R W - MS HERSHEY MED CENTER, PA
item Guthrie, Howard
item HAMMOND J M - MS HERSHEY MED CENTER, PA

Submitted to: Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/14/1994
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 measured the level of atresia during altrenogest-synchronized preovulatory maturation in pigs by quantifying apoptosis in follicle granulosa cells using DNA fluorescence flow cytometry. Follicular fluid (FF) IGFBP-2 levels, measured by ligand blot analysis, IGFBP-2 increased progressively as follicles became more atretic. Level of IGFBP-3 did not differ significantly between healthy and atretic follicles, but among healthy follicles IGFBP-3 increased (P<.01) as follicles approached the time of ovulation. These data suggest that content of IGFBP-2 related to state of follicular health/atresia while IGFBP-3 is related to preovulatory follicular development. 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 better regulate ovulation rate.

Technical Abstract: Insulin-like growth factor-binding protein (IGFBP) levels were compared with indicators of follicular maturation and atresia in individual follicles of the porcine ovary. Growth of an ovulatory cohort of follicles was initiated by withdrawal of the progestin agonist, Altrenogest. Individual follicles were isolated on days 1, 3, 5, and 7 after progestin withdrawal. Atretic follicles were identified by the presence of low, hypodiploid levels of DNA in > 10% of their granulosa cells using flow cytometry. The follicular fluid (FF) level of IGFBP-3 did not differ significantly between healthy and atretic medium-sized (3-6 mm) follicles and was not significantly correlated with percentage of granulosa cells containing hypodiploid levels of DNA (%A0, r= -.181), or with endocrine parameters such as FF concentrations of estradiol (E2) and androstenedione (A4). However, among healthy follicles IGFBP-3 increased (P<.01) between days 1 and 7 and was positively correlated with follicle diameter (r=.513, P<.05), and FF concentration of progesterone (P4)(r=.556, P<.01), indicators of degree of follicular maturation. FF IGFBP-2 levels were 3-fold greater (P<.01) in atretic than in healthy medium-sized follicles and IGFBP-2, was correlated with %A0 cells (r=.729, P<.001). Among healthy follicles, FF IGFBP-2 did not differ significantly among days and was not significantly correlated with follicle diameter. These data suggest that content of IGFBP-2 related to state of follicular health/atresia while IGFBP-3 is related to preovulatory follicular development.