OOPLASMECTOMY HAS NO INFLUENCE ON FSH-INDUCED EXPANSION OF BOVINE CUMULUS INVESTMENT IN-VITRO

Bovine cumulus-oocyte complexes with or without attached pieces of the mural stratum granulosum were matured with or without FSH in vitro fo r 24 h. Some complexes were ooplasmectomized (removal of ooplasm) at t he onset of culture or after 9 h of culture, and in others the complet e oocyte, including the zona pellucida, was removed. At the end of cul ture, the degree and morphology of corona and cumulus expansion were d etermined by a subjective scoring system, transmission electron micros copy followed by computerized image analysis, or scanning electron mic roscopy. In the absence of FSH no expansion was seen. In the presence of FSH, hyaluronidase-sensitive cumulus expansion was observed in inta ct complexes and complexes ooplasmectomized after 9 h of culture. In c omplexes ooplasmectomized at the start of culture, hyaluronidase-insen sitive expansion of the corona compartment was seen as well. A similar reaction was found in free corona and cumulus cell masses cultured in the presence or absence of oocytes. Mural granulosa in intact and oop lasmectomized complexes expanded only slightly under the influence of FSH and exhibited no hyaluronidase sensitivity. Ooplasmectomy at the s tart of culture increased the frequency of ruffled cell membranes and decreased the occurrence of intercellular bridges as compared with unm anipulated complexes cultured under corresponding conditions. It is co ncluded that FSH-induced cumulus expansion and hyaluronidase-sensitive extracellular mucus production of bovine cumulus investment in vitro are not dependent on the oocyte, except for minor changes in the surfa ce morphology of the cumulus cells.