Enzyme cytochemical and morphometrical analyses of gap junctions in rabbit ovarian granulosa cells during follicle maturation and ovulatory process.

Abstract

The gap junctions in rabbit ovarian granulosa cells were examined by morphometrical and cytochemical studies for adenylate cyclase activity during the follicle maturation and ovulatory process. The surface gap junctions, which were observed very early even in the preantral follicles with two layers of granulosa cells, increased significantly in both size and frequency during the follicle maturation. After the ovulatory stimulation by human chorionic gonadotropin (hCG), the surface gap junctions decreased significantly until 9hr, the time just prior to ovulation. In comparison, the annular gap junctions, which were first observed at around the time of antrum formation and frequently found in the neighborhood of surface gap junctions, increased significantly to a maximal level 4hr after the hCG stimulation and subsequently decreased. The adenylate cyclase activity was usually shown on the cytoplasmic side of surface gap junctions during the follicle maturation and ovulatory process. However, no enzyme activity was detected on the inside membrane of some annular gap junctions with bizarre forms or electronlucent contents. Collectively, present cytochemical and morphometrical results suggest that surface gap junctions are infolded in the form of annular gap junctions by the endocytotic process and degraded into the cytoplasma, in accordance with the follicle maturation and ovulation.