CHANGES IN GAP JUNCTION CONNEXIN-43 MESSENGER-RIBONUCLEIC-ACID LEVELSASSOCIATED WITH RAT OVARIAN FOLLICULAR DEVELOPMENT AS DEMONSTRATED BYINSITU HYBRIDIZATION

OBJECTIVE: The purpose was to evaluate the changes in gap junction con nexin-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 synchronizatio n of cellular events, including ovarian follicular development. Ovaria n gap junctions consist of the protein connexin-43. STUDY DESIGN: We u sed the hypophysectomized immature rat treated with estrogen or gonado tropins as a model to study the ovarian regulation of connexin-43 mess enger ribonucleic acid. In situ hybridization with radiolabeled ribopr obes was used to localize and quantitate connexin-43 messenger ribonuc leic acid. RESULTS: We demonstrated that connexin-43 messenger ribonuc leic acid was localized to follicular granulosa cells. Estrogen signif icantly up-regulated connexin-43 messenger ribonucleic acid (91%), whe reas gonadotropins that stimulate ovulation and corpus luteum formatio n completely down-regulated the connexin-43 gene. These results correl ate closely with previous immunohistochemical studies of connexin-43 p rotein. CONCLUSION: The positive correlation between follicular develo pment and granulosa cell content of connexin-43 messenger ribonucleic acid is caused by transcriptional activation of the gap junction conne xin-43 gene, posttranscriptional stability of connexin-43 messenger ri bonucleic acid, or both. Future studies will determine the molecular m echanisms of hormonal regulation of the connexin-43 gene.