Abstract
Ovaries from newborn female mice were cultured for 4 or 8 days in Eagle's minimum essential medium supplemented with pregnant mare's serum gonadotrophin (PMSG) at a concentra-tion of 0, 2, 10 or 50IU/ml. At the beginning of culture, most oocytes in the ovaries were smaller than 20μm in diameter and no zona pellucida was formed around them. During 4 days of culture, promotion of oocyte growth by PMSG (10 and 50IU/ml) was observed. After 8 days, proportions of oocytes with a continuous zona pellucida were significantly higher in PMSG-supplementation groups. In the cultured ovaries, however, the multilayered granulosa cells, that could be often seen around growing oocytes in 8-day-old mouse ovaries, were not observed at all irrespective of the presence of PMSG. These results suggest that PMSG promotes early oocyte growth and zona pellucida formation of oocytes in neonatal mice, although it has a little effect on the proliferation of granulosa cells.
