Molecular biological methods for monitoring oocyte maturation and in vitro fertilization in bitches

Oocytes were collected from ovaries of bitches, at various stages of the oestrous cycle, after routine sterilization. Cumulus-enclosed oocytes were cultured for 0-72 h in a modified M-199 medium containing 10% oestrous bitch serum and 20 micrograms oestradiol ml-1. For oocytes surrounded by two or more layers of cumulus cells, an increase in the expression of mRNA transcripts for zona pellucida glycoprotein 3 (ZP3) was seen and reached peak levels after 48 h culture in vitro. Histological assessment showed that 39% of these oocytes had extruded their first polar body after 24 h culture in vitro. When these in vitro matured oocytes were transferred to oviduct cell monolayers and inseminated with fresh dog spermatozoa in Medium-199 supplemented with 10% fetal calf serum and 50 mg gentamicin sulfate ml-1, penetration of the zona pellucida started 1 h after insemination for oocytes that had been cultured for 48 and 72 h. At 12 h after insemination both male and female pronuclei were seen in 37.5% and 20% of the oocytes incubated for 48 and 72 h, respectively. No further development was seen.