Further studies of the effects of follicular fluid and membrana granulosa cells on the spontaneous maturation of pig oocytes.

Liberated cumulus-enclosed pig oocytes were cultured either alone in follicular fluid or with membrana granulosa cells in a complex serum based medium. After 24 h, oocytes were air-dried for cytogenetic analysis, meiotic stage was scored, and viability of granulosa cells was determined. Neither the release from meiotic arrest nor the progression of maturation to metaphase II was significantly inhibited by either of these follicular components. Co-culture of membrana granulosa cells and oocytes significantly stimulated maturation in one experimental series, while viability of the somatic cells was maintained in all experiments. These results do not support the concept of a stable oocyte maturation inhibitor of granulosa cell origin in follicular fluid.