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

Abstract

Androgens play an essential role as autocrine or paracrine agents in ovarian follicular growth, maturation and luteinization. The aim of this study was to describe the normal cellular distribution of androgen receptors in the canine ovary at different stages of the oestrous cycle. Samples of both ovaries were obtained from 34 dogs, including six pregnant animals and three that had just produced litters. Presence of androgen receptors was visualized by immunohistochemistry on paraffin wax sections using a polyclonal antibody. Nuclear staining for androgen receptors was observed in the surface epithelium, cortical tubules, rete ovarii, follicle cells, thecal cells, luteal cells, granulosa cell cords and ovarian stroma, indicating that androgens have important roles in ovarian function in bitches. In theca interna cells of tertiary follicles, androgen production seems to be more important than androgen receptivity, as immunostaining for androgen receptors in these cells was weak compared with that in other ovarian stromal cells. In primordial and primary follicles, the immunostaining for androgen receptors was rather weak, indicating that androgens are of minor importance in early preantral 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 correlated with serum progesterone concentrations, although local actions of progesterone on androgen receptors in corpora lutea cannot be excluded. In general, few correlations were found between immunostaining for androgen receptors and serum sex steroid concentrations, indicating that other factors regulate androgen receptors in the canine ovary.