Changes in Cortical Granule Distribution within Bovine Oocytes during Maturation and Fertilization In Vitro

Abstract

The distributional changes of cortical granules (CGs) in bovine oocytes during maturation and fertilization in vitro were histochemically examined with lectin. Lens culinaris agglutinin (LCA)-reactive CGs were densely distributed as irregular aggregates of particles throughout the peripheral cytoplasm of every oocyte immediately after collection, while a few were individually dispersed (type I). As the stages of oocyte maturation proceeded, the aggregated CGs collapsed (type II), and the CGs became distributed individually in the cortical cytoplasm (type III). When matured oocytes were inseminated, the CGs completely disappeared in 40, 48 and 69% of oocytes at 3, 6 and 12 h after insemination (type V), respectively. However, type IV oocytes with very few CGs in the inner cytoplasm were always present in about 10% at any time after insemination.