FSH-stimulated follicular secretions enhance oocyte maturation in pigs.
Follicular secretions can support cytoplasmic maturation in vitro in the pig. The effects of follicular secretions stimulated in vitro by different combinations of gonadotropins and over different culture periods on cytoplasmic maturation of the pig oocyte were studied. In Experiment 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 obtained conditioned media were used for oocyte maturation. Oocytes cultured in conditioned medium harvested after treatment of follicular shells with 2.5 mug/ml FSH (FSH-stimulated conditioned medium) yielded a higher percentage of male pronuclear formation than those matured in conditioned medium harvested after culture of follicular shells with a combination of hormones (2.5mug/ml FSH, 2.5 mug/ml LH and 20 ng/ml PRL, 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 cultured 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 male pronuclear formation in oocytes matured in these 2 conditioned media did not differ (P=0.65), but were higher than those of oocytes matured in fresh control medium (P<0.03). It is concluded that factors secreted by follicular cells stimulated by FSH alone provide better support for full oocyte maturation in the pig than by combined FSH, LH and PRL treatment.
Ding
J
J
Department of Animal Science, Faculty of Agriculture and Forestry University of Alberta, Edmonton, Alberta, Canada T6G 2P5.
Foxcroft
G R
GR