Effects of granulosa cells and gonadotrophins on maturation of rabbit oocytes in vitro.

Rabbit oocyte maturation was induced by i.v. injection of 100 mU/HCG. Six hours later the animals were sacrificed, their granulosa cells cultured 7-10 days and their oocytes incubated in different media for 5-6 h. The oocytes were then examined microscopically. The appearance of a polar body was taken as an indication that maturation had progressed. The results presented show that maturation of rabbit oocytes can be inhibited by granulosa cells in vitro (OMI = oocyte maturation inhibitor), the activity of OMI is influenced by gonadotrophins and cumulus cells have a facilitatory effect on OMI. The results give the first indication that OMI exists in rabbits and may contribute to the discussion about the existence of OMI in other species (e.g. the pig).