FSH-STIMULATED FOLLICULAR SECRETIONS ENHANCE OOCYTE MATURATION IN PIGS

Follicular secretions can support cytoplasmic maturation in vitro in t he pig. The effects of follicular secretions stimulated in vitro by di fferent combinations of gonadotropins and over different culture perio ds on cytoplasmic maturation of the pig oocyte were studied. In Experi ment 1, follicular shells (including theca and mural granulosa cells) from 5 to 7-mm follicles were cultured in vitro under the stimulation of different combinations of gonadotropins for 48 h, and then the obta ined conditioned media were used for oocyte maturation. Oocytes cultur ed in conditioned medium harvested after treatment of follicular shell s with 2.5 mu g/ml FSH (FSH-stimulated conditioned medium) yielded a h igher percentage of male pronuclear formation than those matured in co nditioned medium harvested after culture of follicular shells with a c ombination of hormones (2.5 mu g/ml FSH, 2.5 mu g/ml LH and 20 ng/ml P RL, FSH-LH-PRL-stimulated conditioned medium; 54. 1 vs 28.5%; P=0.001) . Addition of the combination of FSH, LH and PRL during the period of oocyte maturation marginally improved male pronuclear formation rates (41.3 vs 55.6%; P=0.06). In Experment 2, follicular shells were cultur ed under the stimulation of FSH only. Conditioned media were harvested after the first 24 h and the second 24 h of culture. The rates of mal e pronuclear formation in oocytes matured in these 2 conditioned media did not differ (P=0.65), but were higher than those of oocytes mature d in fresh control medium (P=0.03). It is concluded that factors secre ted by follicular cells stimulated by FSH alone provide better support for full oocyte maturation in the pig than by combined FSH, LH and PR L treatment.