LOCATION AND DEVELOPMENTAL REGULATION OF ANDROGEN RECEPTOR IN PRIMATEOVARY

Locally produced androgens act via granulosa cell androgen receptors t o modulate follicular responsiveness to gonadotrophins and thereby con tribute to the paracrine regulation of ovarian function. We used quant itative androgen receptor immunocytochemistry to assess androgen recep tor distribution in relation to pre-ovulatory follicular development i n the common marmoset (Callithrix jacchus), a New World primate that o vulates two to four follicles in each similar to 28 day ovarian cycle. Ovaries from four adult females in the late follicular phase and from four in the luteal phase were fixed in 4% paraformaldehyde and subjec ted to an immunocytochemical analysis using a polyclonal androgen rece ptor antibody with detection by a standard avidin-biotin-peroxidase te chnique for alkaline phosphatase. Specific androgen receptor immunosta ining occurred mainly in granulosa cell nuclei, with little or no spec ific staining in theca, stroma or oocytes. Granulosa cell androgen rec eptor immunostaining was most abundant in healthy preantral/early antr al follicles, being low or absent from pre-ovulatory follicles and cor pora lutea. Differences in granulosa cell androgen receptor immunostai ning between immature (0.1-1.0 mm diameter) and preovulatory (greater than or equal to 2.0 mm diameter) follicles were quantified using a vi deodensitometric analysis of grey-scale values. Readings were taken fr om the granulosa cell layers of 53 immature follicles and 10 pre-ovula tory follicles in late follicular phase ovaries. The average androgen receptor level in granulosa cells of immature follicles proved to be 4 .2-fold higher (P < 0.01) than that in granulosa cells of pre-ovulator y follicles. Because other evidence suggests that paracrine androgen a ction in granulosa cells converts from stimulation to inhibition as fo llicles mature, we speculate that a development-related reduction in a ndrogen receptor numbers serves to 'protect' granulosa cells against t he inhibitory action of androgen, thereby promoting pre-ovulatory foll icular dominance in primate ovarian cycles.