Detection and in vivo hormonal regulation of rat ovarian type I and type II interleukin-I receptor mRNAs: increased expression during the periovulatory period.

OBJECTIVE

To study the expression, localization, and in vivo hormonal regulation of type I and type II interleukin-1 (IL-1) receptors in the rat ovary.

METHODS

Segments of the cDNAs for rat type I and type II IL-1 receptors were cloned and used as probes in RNase protection assays and in situ hybridization. Tissues obtained from immature rats and hormonally treated rat ovaries were examined.

RESULTS

Type I IL-1 receptor (IL-1R(1)) was ubiquitously expressed in rat tissues, including granulosa cells prepared from immature ovaries, whereas type II IL-1 receptor (IL-1R(2)) expression was restricted to macrophages, thymus, and lung. Hypophysectomy and subsequent treatment with FSH and/or diethylstilbestrol did not alter significantly the abundance of IL-1R(1) transcripts in the whole ovary. However, the relative amount of ovarian IL-1R(1) transcripts increased 7.3-fold 6 hours after the administration of hCG to pregnant mare serum gonadotropin-primed immature rats. During this time, IL-1R(1) mRNA was localized primarily in the granulosa cells. The increased expression of IL-1R(1) persisted 24 hours after hCG administration but declined to baseline by 48 hours. Ovarian expression of IL-1R(2) mRNA was observed only before ovulation in amounts that were approximately 70-fold lower than IL-1R(1).

CONCLUSION

The increased intraovarian expression of IL-1R(1) in granulosa cells during the periovulatory period implies that this cell type has a heightened receptivity to IL-1 and provides further indirect evidence that this cytokine is involved in the ovulatory process.