Abstract
Dibutyryl cyclic adenosine 3', 5'-monophosphate (dbcAMP) and calmodulin antagonist (W7) inhibit the occurrence of spontaneous germinal vesicle breakdown (GVBD) of isolated mouse oocytes in culture. The effect on the morphological profile of germinal vesicle (GV) of cumulus-free mouse oocytes with dbcAMP and W7 was examined. Striking changes in the oocytes occurred when incubated with dbcAMP and W7. In oocytes incubated with dbcAMP at a concentration of 100μM for 3 h, the distinct Hoechst dye-derived fluorescence in the nucleolus disappeared while the nuclear envelope developed an undulatory contour. The chromosomes started to condense and a large vacuole appeared within the nucleolus. These results suggest that dbcAMP did not suppress the initial phase of GVBD of mouse oocytes. In oocyte treated with W7, the smooth nuclear envelope developed an undulatory contour with fragmentation of the nucleolus into one large segment and many small pieces. The nucleolus retained the Hoechst dye-derived fluorescent staining. The present findings suggest that dbcAMP and W7 act at different loci in inhibiting spontaneous induction of GVBD of mouse oocytes in culture.
