CHANGES IN FOLLICULAR ENDOCRINOLOGY DURING FINAL MATURATION OF PORCINE OOCYTES

Thirty-one gilts were ovariectomized between 21 and 34 hr after the onset of estrus to compare changes in follicular endocrinology with stages of oocyte maturation. Oocytes were recovered from 6 to 8 mm follicles and classified by stage of meiosis. Remaining follicular fluid was assayed for steroids and dermatan sulfate. Amounts of prostaglandin F2α (PGF2α) and E2 (PGE2) were measured in intramural tissues. Coincident with germinal vesicle breakdown, the follicular content of all steroids except testosterone decreased (P<.05). As oocytes approached metaphase II, the amount of progesterone within follicles increased (P<.05), and estradiol continued to decrease (P<.05). The pattern of dermatan sulfate content was biphasic and peaked at germinal vesicle breakdown and anaphase stages. Amounts of PGF2α and PGE2 within intramural tissues increased (P<.05) throughout oocyte maturation. Follicular atresia was evident during estrus; however, more (P<.05) atretic follicles were recovered at germinal vesicle than metaphase II stages (20 vs 3%, respectively). Follicular development, within a gilt, was skewed (P<.05) and classification of follicles by hormone content demonstrated that a majority were more mature than a minority of less mature follicles. These data suggest that follicular maturation and oocyte development are highly correlated in swine. Furthermore, partitioning the follicular variability by hour and stage of oocyte maturation allowed for more precise assessment of follicular endocrinology than previously reported. © 1990.