Hormonal influence on the secretory immune system of the eye: androgen regulation of secretory component levels in rat tears.

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Abstract
The present study examined the influence of gender and steroid hormones on the level of free secretory component (SC) in tears of rats. The SC concentration in tears of male rats was approximately five-fold greater than that found in tears of females. This difference could not be accounted for by variations in tear volume or a suppression of tear SC content in female rats during certain stages of the estrous cycle. Rather, the elevated level of SC in tears of males appeared to be due to the effect of androgens. Castration of male, but not female, rats resulted in a time-dependent decrease in the SC content of tears. Administration of testosterone to orchiectomized rats reversed this decline and induced a time- and dose-dependent increase in the tear SC concentration. This response appeared specific for androgens, because treatment of orchiectomized rats with progesterone, estradiol, or cortisol had no effect on total tear SC. Consistent with this hypothesis was our finding that injection of castrated male rats with 5 alpha-dihydrotestosterone also raised the tear SC concentration. Of interest, the androgen-induced increase of the SC level in tears was not accompanied by similar changes in total tear protein. These results suggest that androgens may influence the production and/or secretion of SC by ocular tissues. Furthermore, our findings indicate that androgens play a role in the ocular secretory immune system of the rat.