Localization, Cyclic Variation, and Hormonal Regulation of a Potential Determinant

It is hypothesized that the intraovarian interleukin (IL)-1 sys-tem plays a prominent role in the regulation of follicular devel-opment and ovulation. A central component of the intraovarian IL-1 system is the IL-1 receptor antagonist (IL-1RA), a protein acting as a pure IL-1 receptor antagonist and one for which intracellular (icIL-1RA) and secretory (sIL-1RA) varieties have been described. It was the objective of this study to explore rat ovarian IL-1RA gene expression, to establish the identity and relative abundance of its alternative transcripts, to study its cel-lular localization, to determine its cyclic variation, and to assess its hormonal regulation. Protected IL-1RA cDNA fragments cor-responding to either sIL-1RA or icIL-1RA were barely detectable in untreated whole ovarian tissue of immature rat origin. How-ever, sIL-1RA transcripts reached a maximal value (3.3-fold in