Changes in gap junction connexin-43 messenger ribonucleic acid levels associated with rat ovarian follicular development as demonstrated by in situ hybridization.

Abstract

The purpose was to evaluate the changes in gap junction connexin-43 messenger ribonucleic acid levels associated with rat ovarian follicular development. Gap junctions connect the plasma membranes of adjacent cells through cell-to-cell channels, allowing synchronization of cellular events, including ovarian follicular development. Ovarian gap junctions consist of the protein connexin-43. We used the hypophysectomized immature rat treated with estrogen or gonadotropins as a model to study the ovarian regulation of connexin-43 messenger ribonucleic acid. In situ hybridization with radiolabeled riboprobes was used to localize and quantitate connexin-43 messenger ribonucleic acid. We demonstrated that connexin-43 messenger ribonucleic acid was localized to follicular granulosa cells. Estrogen significantly up-regulated connexin-43 messenger ribonucleic acid (91%), whereas gonadotropins that stimulate ovulation and corpus luteum formation completely down-regulated the connexin-43 gene. These results correlate closely with previous immunohistochemical studies of connexin-43 protein. The positive correlation between follicular development and granulosa cell content of connexin-43 messenger ribonucleic acid is caused by transcriptional activation of the gap junction connexin-43 gene, posttranscriptional stability of connexin-43 messenger ribonucleic acid, or both. Future studies will determine the molecular mechanisms of hormonal regulation of the connexin-43 gene.