Immunolocalization of androgen receptor and steroidogenic enzymes in cumuli oophori of pre- and post-ovulatory rats

SummaryImmunolocalization of 3β-hydroxysteroid dehydrogense (3β-HSD), cytochrome P450c17 (P450c17) and androgen receptor (AR) were investigated in rat cumuli oophori (COCs) of late pre-ovulatory follicles and in post-ovulatory COCs bearing fertilized oocytes. A gradient of intensity of 3β-HSD immunolabelling was observed in the granulosa layer of pre-ovulatory follicles, with almost negative immunolabelling in COCs and with the strongest immunoreaction in the mural granulosa cells. Post-ovulatory COCs showed strong 3β-HSD immunolabelling in the peripheral regions and weak labelling near the oocyte, suggestive of responsiveness of cumulus cells to an anti-luteinizing effect exerted by the fertilized oocyte. In pre-ovulatory follicles, a weak P450c17 immunopositivity was limited to expanded cumulus granulosa cells and the positive labelling persisted in post-ovulatory COCs. P450c17 immunopositivity was also found in ampullary epithelial cells. A strong AR immunopositivity was confined mainly to the COCs in pre-ovulatory follicles and a similar immunoreaction was present in the granulosa cells of ovulated COCs. Simultaneous AR and cytochrome P450c17 immunolabelling in the pre- and post-ovulatory COCs is suggestive of an intra- and paracrine androgen regulation of the cumulus granulosa cell function.