Rat ovarian interleukin-1α: Interleukin-1-dependent in vitro expression

Evidence exists supporting the possibility that intraovarian interleukin-1 (IL-1) may play an intermediary role in the periovulatory cascade. Although the existence of a mammalian intraovarian IL-1 system has been convincingly demonstrated, most efforts have focused on the possibility that the mammalian ovary is a site of IL-1b production, reception, and action. The objective of this study was to explore the possibility of ovarian IL-1a expression, characterize its pattern of expression by cultured ovarian cells, and study its hormonal regulation. The basal in vitro expression of IL-1a by cultured whole ovarian dispersates from immature rats increased spontaneously, reaching a peak (sixfold increase over untreated controls) at 4 h. Treatment with an IL-1 receptor antagonist (IL-1RA), human chorionic gonadorropin, or IL-1b failed to attenuate the initial 4-h burst of IL-1a expression. By contrast, treatment of whole ovarian dispersates with IL-1b for 48 h resulted in significant upregulation of IL-1a transcripts (60-fold increase). This IL-1b effect was completely blocked by cotreatment with IL- 1RA, thereby suggesting mediation via a specific IL-1 receptor. The IL-1b effect proved to be protein biosynthesis and eicosanoid dependent, nitric oxide independent, and relatively specific in that it was not reproduced by a select series of other granulosa cell agonists.