Immunolocalization of androgen receptors in the canine ovary and their relation to sex steroid hormone concentrations

Androgens play an essential role as autocrine or paracrine agents in ovaria n follicular growth, maturation and luteinization. The aim of this study wa s to describe the normal cellular distribution of androgen receptors in the canine ovary at different stages of the oestrous cycle. Samples of both ov aries were obtained from 34 dogs, including six pregnant animals and three that had just produced litters. Presence of androgen receptors was visualiz ed by immunohistochemistry on paraffin wax sections using a polyclonal anti body. Nuclear staining for androgen receptors was observed in the surface e pithelium, cortical tubules, rete ovarii, follicle cells, thecal cells, lut eal cells, granulosa cell cords and ovarian stroma indicating that androgen s have important roles in ovarian function in bitches. in theca interna cel ls of tertiary follicles, androgen production seems to be more important th an androgen receptivity, as immunostaining for androgen receptors in these cells was weak compared with that in other ovarian stromal cells. In primor dial and primary follicles, the immunostaining for androgen receptors was r ather weak, indicating that androgens are of minor importance in early prea ntral follicles. In follicle cells of larger preantral and antral follicles , the immunostaining for androgen receptors increased with the stage of the follicle. Corpora lutea expressed less immunostaining, which was not corre lated with serum progesterone concentrations, although local actions of pro gesterone on androgen receptors in corpora lutea cannot be excluded. In gen eral, few correlations were found between immunostaining for androgen recep tors and serum sex steroid concentrations, indicating that other factors re gulate androgen receptors in the canine ovary.